From 554d66f6a3157d4e427aef410741365d46b37130 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Fri, 19 Jul 2019 20:14:52 +0800
Subject: [PATCH 01/82] init single-number-iii

---
 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 452182b..9a39431 100644
--- a/README.md
+++ b/README.md
@@ -54,10 +54,10 @@ cargo test
 0191  |[Number of 1 Bits](https://leetcode.com/problems/number-of-1-bits/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/number-of-1-bits.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/number-of-1-bits.py) <br> [Rust](./kamyu104/src/number_of_1_bits.rs) | _O(1)_ | _O(1)_          | Easy           |||
 0201 | [Bitwise AND of Numbers Range](https://leetcode.com/problems/bitwise-and-of-numbers-range/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/bitwise-and-of-numbers-range.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/bitwise-and-of-numbers-range.py) <br> [Rust](./kamyu104/src/bitwise_and_of_numbers_range.rs) | _O(1)_ | _O(1)_ | Medium ||
 0231 | [Power of Two](https://leetcode.com/problems/power-of-two/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/power-of-two.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/power-of-two.py) <br> [Rust](./kamyu104/src/power_of_two.rs) | _O(1)_ | _O(1)_ | Easy | LintCode |
+0260 | [Single Number III](https://leetcode.com/problems/single-number-iii/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/single-number-iii.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/single-number-iii.py) <br> [Rust](./kamyu104/src/single_number_iii.rs) | _O(n)_ | _O(1)_          | Medium         ||
 
 <!-- 
 
-0260 | [Single Number III](https://leetcode.com/problems/single-number-iii/) | [C++](./C++/single-number-iii.cpp) [Python](./Python/single-number-iii.py) | _O(n)_ | _O(1)_          | Medium         ||
 0268| [Missing Number](https://leetcode.com/problems/missing-number/) | [C++](./C++/missing-number.cpp) [Python](./Python/missing-number.py)  | _O(n)_ |  _O(1)_ | Medium         | LintCode ||
 0318| [Maximum Product of Word Lengths](https://leetcode.com/problems/maximum-product-of-word-lengths/) | [C++](./C++/maximum-product-of-word-lengths.cpp) [Python](./Python/maximum-product-of-word-lengths.py)  | _O(n)_ ~ _O(n^2)_ |  _O(n)_ | Medium         || Bit Manipulation, Counting Sort, Pruning|
 0342 | [Power of Four](https://leetcode.com/problems/power-of-four/) | [C++](./C++/power-of-four.cpp) [Python](./Python/power-of-four.py) | _O(1)_ | _O(1)_ | Easy | |

From 9c2ef2c019938e7bdac01a2157b429a88b34c518 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Fri, 19 Jul 2019 20:16:00 +0800
Subject: [PATCH 02/82] update

---
 kamyu104/src/main.rs              |  1 +
 kamyu104/src/single_number_iii.rs | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+)
 create mode 100644 kamyu104/src/single_number_iii.rs

diff --git a/kamyu104/src/main.rs b/kamyu104/src/main.rs
index 83e74a9..f6ffca0 100644
--- a/kamyu104/src/main.rs
+++ b/kamyu104/src/main.rs
@@ -4,4 +4,5 @@ mod power_of_two;
 mod reverse_bits;
 mod single_number;
 mod single_number_ii;
+mod single_number_iii;
 mod template;
diff --git a/kamyu104/src/single_number_iii.rs b/kamyu104/src/single_number_iii.rs
new file mode 100644
index 0000000..8f2e1c2
--- /dev/null
+++ b/kamyu104/src/single_number_iii.rs
@@ -0,0 +1,18 @@
+pub struct Solution {}
+impl Solution {
+    pub fn add(a: i32, b: i32) -> i32 {
+        println!("{}", a + b);
+        return a + b;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_add() {
+        assert_eq!(Solution::add(1, 2), 3);
+        assert_ne!(Solution::add(1, 2), 4);
+    }
+}

From f956209bb4737eca936f6c5d84a2c8765da36ad6 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Fri, 19 Jul 2019 20:21:16 +0800
Subject: [PATCH 03/82] init

---
 kamyu104/src/single_number_iii.rs | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/kamyu104/src/single_number_iii.rs b/kamyu104/src/single_number_iii.rs
index 8f2e1c2..7b921d4 100644
--- a/kamyu104/src/single_number_iii.rs
+++ b/kamyu104/src/single_number_iii.rs
@@ -1,8 +1,7 @@
 pub struct Solution {}
 impl Solution {
-    pub fn add(a: i32, b: i32) -> i32 {
-        println!("{}", a + b);
-        return a + b;
+    pub fn single_number(nums: Vec<i32>) -> Vec<i32> {
+        nums
     }
 }
 
@@ -11,8 +10,7 @@ mod tests {
     use super::*;
 
     #[test]
-    fn test_add() {
-        assert_eq!(Solution::add(1, 2), 3);
-        assert_ne!(Solution::add(1, 2), 4);
+    fn test_single_number() {
+        assert_eq!(Solution::single_number(vec![1,2,1,3,2,5]), vec![3,5]);
     }
 }

From 0e188cc42f204670bd6327ac7a5bfb48db7ad617 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 15:41:02 +0800
Subject: [PATCH 04/82] init sol for single_number_iii

---
 kamyu104/src/power_of_two.rs      |  2 --
 kamyu104/src/single_number_iii.rs | 13 +++++++++++--
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/kamyu104/src/power_of_two.rs b/kamyu104/src/power_of_two.rs
index 949187a..96048a7 100644
--- a/kamyu104/src/power_of_two.rs
+++ b/kamyu104/src/power_of_two.rs
@@ -15,7 +15,6 @@ impl Solution2 {
     }
 }
 
-
 #[cfg(test)]
 mod tests {
     // Note this useful idiom: importing names from outer (for mod tests) scope.
@@ -32,4 +31,3 @@ mod tests {
         assert_eq!(Solution2::is_power_of_two(218), false);
     }
 }
-
diff --git a/kamyu104/src/single_number_iii.rs b/kamyu104/src/single_number_iii.rs
index 7b921d4..d06896c 100644
--- a/kamyu104/src/single_number_iii.rs
+++ b/kamyu104/src/single_number_iii.rs
@@ -1,7 +1,16 @@
+// Time:  O(n)
+// Space: O(1)
+
 pub struct Solution {}
 impl Solution {
     pub fn single_number(nums: Vec<i32>) -> Vec<i32> {
-        nums
+        let x_xor_y: i32 = nums.iter().fold(0, |acc, &num| acc ^ num);
+        let bit: i32 = x_xor_y & -x_xor_y;
+        let mut result = vec![0; 2];
+        for i in nums {
+            result[((i & bit) != 0) as usize] ^= i
+        }
+        result
     }
 }
 
@@ -11,6 +20,6 @@ mod tests {
 
     #[test]
     fn test_single_number() {
-        assert_eq!(Solution::single_number(vec![1,2,1,3,2,5]), vec![3,5]);
+        assert_eq!(Solution::single_number(vec![1, 2, 1, 3, 2, 5]), vec![5, 3]);
     }
 }

From ce474e282adf62f79d21ad79fd2ebdb4d905b79b Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 15:46:34 +0800
Subject: [PATCH 05/82] foreach

---
 kamyu104/src/single_number_iii.rs | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/kamyu104/src/single_number_iii.rs b/kamyu104/src/single_number_iii.rs
index d06896c..5ff36f0 100644
--- a/kamyu104/src/single_number_iii.rs
+++ b/kamyu104/src/single_number_iii.rs
@@ -7,9 +7,8 @@ impl Solution {
         let x_xor_y: i32 = nums.iter().fold(0, |acc, &num| acc ^ num);
         let bit: i32 = x_xor_y & -x_xor_y;
         let mut result = vec![0; 2];
-        for i in nums {
-            result[((i & bit) != 0) as usize] ^= i
-        }
+        nums.iter()
+            .for_each(|i| result[((i & bit) != 0) as usize] ^= i);
         result
     }
 }

From 38bfbb95185e42ca0079ef9c3bd1800b5dc94711 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 15:58:10 +0800
Subject: [PATCH 06/82] add more

---
 kamyu104/src/reverse_bits.rs | 36 +++++++++++++++++++++++++++++++-----
 1 file changed, 31 insertions(+), 5 deletions(-)

diff --git a/kamyu104/src/reverse_bits.rs b/kamyu104/src/reverse_bits.rs
index 69a6b3f..29c5b96 100644
--- a/kamyu104/src/reverse_bits.rs
+++ b/kamyu104/src/reverse_bits.rs
@@ -1,11 +1,24 @@
 // Time : O(logn) = O(32)
 // Space: O(1)
 
-pub struct Solution {}
-impl Solution {
+pub struct Solution1 {}
+impl Solution1 {
     pub fn reverse_bits(mut n: u32) -> u32 {
         let mut result: u32 = 0;
-        for _ in (0..32) {
+        (0..32).for_each(|_| {
+            result <<= 1;
+            result |= n & 1;
+            n >>= 1;
+        });
+        result
+    }
+}
+
+pub struct Solution2 {}
+impl Solution2 {
+    pub fn reverse_bits(mut n: u32) -> u32 {
+        let mut result: u32 = 0;
+        for _ in 0..32 {
             result <<= 1;
             result |= n & 1;
             n >>= 1;
@@ -21,13 +34,26 @@ mod tests {
     #[test]
     fn test_reverse_bits() {
         assert_eq!(
-            Solution::reverse_bits(
+            Solution1::reverse_bits(
+                u32::from_str_radix("00000010100101000001111010011100", 2).unwrap()
+            ),
+            u32::from_str_radix("00111001011110000010100101000000", 2).unwrap()
+        );
+        assert_eq!(
+            Solution1::reverse_bits(
+                u32::from_str_radix("11111111111111111111111111111101", 2).unwrap()
+            ),
+            u32::from_str_radix("10111111111111111111111111111111", 2).unwrap()
+        );
+
+        assert_eq!(
+            Solution2::reverse_bits(
                 u32::from_str_radix("00000010100101000001111010011100", 2).unwrap()
             ),
             u32::from_str_radix("00111001011110000010100101000000", 2).unwrap()
         );
         assert_eq!(
-            Solution::reverse_bits(
+            Solution2::reverse_bits(
                 u32::from_str_radix("11111111111111111111111111111101", 2).unwrap()
             ),
             u32::from_str_radix("10111111111111111111111111111111", 2).unwrap()

From 28ca1b78db84e7b6c2fdd997cf10b851178bd302 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 16:08:38 +0800
Subject: [PATCH 07/82] init sol2

---
 kamyu104/src/single_number_iii.rs | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/kamyu104/src/single_number_iii.rs b/kamyu104/src/single_number_iii.rs
index 5ff36f0..690e182 100644
--- a/kamyu104/src/single_number_iii.rs
+++ b/kamyu104/src/single_number_iii.rs
@@ -1,8 +1,20 @@
 // Time:  O(n)
 // Space: O(1)
 
-pub struct Solution {}
-impl Solution {
+pub struct Solution1 {}
+impl Solution1 {
+    pub fn single_number(nums: Vec<i32>) -> Vec<i32> {
+        let x_xor_y: i32 = nums.iter().fold(0, |acc, &num| acc ^ num);
+        let bit: i32 = x_xor_y & -x_xor_y;
+        let mut result = vec![0; 2];
+        nums.iter()
+            .for_each(|i| result[((i & bit) != 0) as usize] ^= i);
+        result
+    }
+}
+
+pub struct Solution2 {}
+impl Solution2 {
     pub fn single_number(nums: Vec<i32>) -> Vec<i32> {
         let x_xor_y: i32 = nums.iter().fold(0, |acc, &num| acc ^ num);
         let bit: i32 = x_xor_y & -x_xor_y;
@@ -19,6 +31,7 @@ mod tests {
 
     #[test]
     fn test_single_number() {
-        assert_eq!(Solution::single_number(vec![1, 2, 1, 3, 2, 5]), vec![5, 3]);
+        assert_eq!(Solution1::single_number(vec![1, 2, 1, 3, 2, 5]), vec![5, 3]);
+        assert_eq!(Solution2::single_number(vec![1, 2, 1, 3, 2, 5]), vec![5, 3]);
     }
 }

From cfc62422ef8307935921072afb6f24e666d0154c Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 16:24:36 +0800
Subject: [PATCH 08/82] add

---
 kamyu104/src/single_number_iii.rs | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/kamyu104/src/single_number_iii.rs b/kamyu104/src/single_number_iii.rs
index 690e182..b00d373 100644
--- a/kamyu104/src/single_number_iii.rs
+++ b/kamyu104/src/single_number_iii.rs
@@ -4,7 +4,12 @@
 pub struct Solution1 {}
 impl Solution1 {
     pub fn single_number(nums: Vec<i32>) -> Vec<i32> {
+        // Xor all the elements to get x ^ y.
         let x_xor_y: i32 = nums.iter().fold(0, |acc, &num| acc ^ num);
+
+        // Get the last bit where 1 occurs by "x & ~(x - 1)"
+        // Because -(x - 1) = ~(x - 1) + 1 <=> -x = ~(x - 1)
+        // So we can also get the last bit where 1 occurs by "x & -x"
         let bit: i32 = x_xor_y & -x_xor_y;
         let mut result = vec![0; 2];
         nums.iter()
@@ -16,12 +21,25 @@ impl Solution1 {
 pub struct Solution2 {}
 impl Solution2 {
     pub fn single_number(nums: Vec<i32>) -> Vec<i32> {
-        let x_xor_y: i32 = nums.iter().fold(0, |acc, &num| acc ^ num);
+        // Xor all the elements to get x ^ y.
+        let mut x_xor_y: i32 = 0;
+        for i in nums.iter() {
+            x_xor_y ^= i;
+        }
+
+        // Get the last bit where 1 occurs.
         let bit: i32 = x_xor_y & -x_xor_y;
-        let mut result = vec![0; 2];
-        nums.iter()
-            .for_each(|i| result[((i & bit) != 0) as usize] ^= i);
-        result
+
+        // Get the subset of A where the number has the bit.
+        // The subset only contains one of the two integers, call it x.
+        // Xor all the elements in the subset to get x.
+        let mut x: i32 = 0;
+        nums.iter().for_each(|i| {
+            if i & bit != 0 {
+                x ^= i;
+            }
+        });
+        vec![x, x_xor_y ^ x]
     }
 }
 
@@ -32,6 +50,6 @@ mod tests {
     #[test]
     fn test_single_number() {
         assert_eq!(Solution1::single_number(vec![1, 2, 1, 3, 2, 5]), vec![5, 3]);
-        assert_eq!(Solution2::single_number(vec![1, 2, 1, 3, 2, 5]), vec![5, 3]);
+        assert_eq!(Solution2::single_number(vec![1, 2, 1, 3, 2, 5]), vec![3, 5]);
     }
 }

From 14fed544c3b04c0a1276d3d38fae8238cc0bacf1 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 16:26:19 +0800
Subject: [PATCH 09/82] clean

---
 kamyu104/src/power_of_two.rs      | 1 -
 kamyu104/src/single_number_iii.rs | 1 +
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/kamyu104/src/power_of_two.rs b/kamyu104/src/power_of_two.rs
index 96048a7..8cc3096 100644
--- a/kamyu104/src/power_of_two.rs
+++ b/kamyu104/src/power_of_two.rs
@@ -17,7 +17,6 @@ impl Solution2 {
 
 #[cfg(test)]
 mod tests {
-    // Note this useful idiom: importing names from outer (for mod tests) scope.
     use super::*;
 
     #[test]
diff --git a/kamyu104/src/single_number_iii.rs b/kamyu104/src/single_number_iii.rs
index b00d373..bf9e88f 100644
--- a/kamyu104/src/single_number_iii.rs
+++ b/kamyu104/src/single_number_iii.rs
@@ -50,6 +50,7 @@ mod tests {
     #[test]
     fn test_single_number() {
         assert_eq!(Solution1::single_number(vec![1, 2, 1, 3, 2, 5]), vec![5, 3]);
+        
         assert_eq!(Solution2::single_number(vec![1, 2, 1, 3, 2, 5]), vec![3, 5]);
     }
 }

From 7178f9d4ee229b2715624ce705325c7afbcb315d Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 16:26:46 +0800
Subject: [PATCH 10/82] clean

---
 kamyu104/src/single_number_iii.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kamyu104/src/single_number_iii.rs b/kamyu104/src/single_number_iii.rs
index bf9e88f..38b19c9 100644
--- a/kamyu104/src/single_number_iii.rs
+++ b/kamyu104/src/single_number_iii.rs
@@ -50,7 +50,7 @@ mod tests {
     #[test]
     fn test_single_number() {
         assert_eq!(Solution1::single_number(vec![1, 2, 1, 3, 2, 5]), vec![5, 3]);
-        
+
         assert_eq!(Solution2::single_number(vec![1, 2, 1, 3, 2, 5]), vec![3, 5]);
     }
 }

From 7389e3464e7fd4c6a2d63a603103b6f2c4b234af Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 16:30:25 +0800
Subject: [PATCH 11/82] init missing_number

---
 kamyu104/src/main.rs           | 1 +
 kamyu104/src/missing_number.rs | 1 +
 2 files changed, 2 insertions(+)
 create mode 100644 kamyu104/src/missing_number.rs

diff --git a/kamyu104/src/main.rs b/kamyu104/src/main.rs
index f6ffca0..855a106 100644
--- a/kamyu104/src/main.rs
+++ b/kamyu104/src/main.rs
@@ -1,4 +1,5 @@
 mod bitwise_and_of_numbers_range;
+mod missing_number;
 mod number_of_1_bits;
 mod power_of_two;
 mod reverse_bits;
diff --git a/kamyu104/src/missing_number.rs b/kamyu104/src/missing_number.rs
new file mode 100644
index 0000000..8b13789
--- /dev/null
+++ b/kamyu104/src/missing_number.rs
@@ -0,0 +1 @@
+

From 810d3bdc13536bb9c2749daddc888211bcdc5458 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 16:34:38 +0800
Subject: [PATCH 12/82] add

---
 kamyu104/src/missing_number.rs | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/kamyu104/src/missing_number.rs b/kamyu104/src/missing_number.rs
index 8b13789..4b698a5 100644
--- a/kamyu104/src/missing_number.rs
+++ b/kamyu104/src/missing_number.rs
@@ -1 +1,17 @@
+pub struct Solution {}
+impl Solution {
+    pub fn missing_number(nums: Vec<i32>) -> i32 {
+        0
+    }
+}
 
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_missing_number() {
+        assert_eq!(Solution::missing_number(vec![3, 0, 1]), 2);
+        assert_eq!(Solution::missing_number(vec![9, 6, 4, 2, 3, 5, 7, 0, 1]), 8);
+    }
+}

From 076b0cc998ccd751ea010856221651ca75aa114d Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 16:37:26 +0800
Subject: [PATCH 13/82] add more

---
 kamyu104/src/missing_number.rs | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/kamyu104/src/missing_number.rs b/kamyu104/src/missing_number.rs
index 4b698a5..e8623ec 100644
--- a/kamyu104/src/missing_number.rs
+++ b/kamyu104/src/missing_number.rs
@@ -1,5 +1,16 @@
-pub struct Solution {}
-impl Solution {
+// Time:  O(n)
+// Space: O(1)
+pub struct Solution1 {}
+impl Solution1 {
+    pub fn missing_number(nums: Vec<i32>) -> i32 {
+        0
+    }
+}
+
+// Time:  O(n)
+// Space: O(n)
+pub struct Solution2 {}
+impl Solution2 {
     pub fn missing_number(nums: Vec<i32>) -> i32 {
         0
     }
@@ -11,7 +22,16 @@ mod tests {
 
     #[test]
     fn test_missing_number() {
-        assert_eq!(Solution::missing_number(vec![3, 0, 1]), 2);
-        assert_eq!(Solution::missing_number(vec![9, 6, 4, 2, 3, 5, 7, 0, 1]), 8);
+        assert_eq!(Solution1::missing_number(vec![3, 0, 1]), 2);
+        assert_eq!(
+            Solution1::missing_number(vec![9, 6, 4, 2, 3, 5, 7, 0, 1]),
+            8
+        );
+
+        assert_eq!(Solution2::missing_number(vec![3, 0, 1]), 2);
+        assert_eq!(
+            Solution2::missing_number(vec![9, 6, 4, 2, 3, 5, 7, 0, 1]),
+            8
+        );
     }
 }

From e289b51126848987f46d69aeb4f36887ba796c80 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 16:54:36 +0800
Subject: [PATCH 14/82] add missing_number

---
 kamyu104/src/missing_number.rs | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/kamyu104/src/missing_number.rs b/kamyu104/src/missing_number.rs
index e8623ec..dadbedd 100644
--- a/kamyu104/src/missing_number.rs
+++ b/kamyu104/src/missing_number.rs
@@ -3,18 +3,22 @@
 pub struct Solution1 {}
 impl Solution1 {
     pub fn missing_number(nums: Vec<i32>) -> i32 {
-        0
+        let mut num: i32 = 0;
+        for i in 0..nums.len() {
+            num ^= nums[i] ^ (i + 1) as i32;
+        }
+        num
     }
 }
 
 // Time:  O(n)
 // Space: O(n)
-pub struct Solution2 {}
-impl Solution2 {
-    pub fn missing_number(nums: Vec<i32>) -> i32 {
-        0
-    }
-}
+// pub struct Solution2 {}
+// impl Solution2 {
+//     pub fn missing_number(nums: Vec<i32>) -> i32 {
+//         0
+//     }
+// }
 
 #[cfg(test)]
 mod tests {
@@ -28,10 +32,10 @@ mod tests {
             8
         );
 
-        assert_eq!(Solution2::missing_number(vec![3, 0, 1]), 2);
-        assert_eq!(
-            Solution2::missing_number(vec![9, 6, 4, 2, 3, 5, 7, 0, 1]),
-            8
-        );
+        // assert_eq!(Solution2::missing_number(vec![3, 0, 1]), 2);
+        // assert_eq!(
+        //     Solution2::missing_number(vec![9, 6, 4, 2, 3, 5, 7, 0, 1]),
+        //     8
+        // );
     }
 }

From a60b3905c039897305dee3ea417ae8f2060255ab Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 16:57:36 +0800
Subject: [PATCH 15/82] add mroe

---
 kamyu104/src/missing_number.rs | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/kamyu104/src/missing_number.rs b/kamyu104/src/missing_number.rs
index dadbedd..cb9e37e 100644
--- a/kamyu104/src/missing_number.rs
+++ b/kamyu104/src/missing_number.rs
@@ -20,6 +20,24 @@ impl Solution1 {
 //     }
 // }
 
+// Time:  O(n)
+// Space: O(1)
+// pub struct Solution3 {}
+// impl Solution3 {
+//     pub fn missing_number(nums: Vec<i32>) -> i32 {
+//         0
+//     }
+// }
+
+// Time:  O(n)
+// Space: O(1)
+// pub struct Solution4 {}
+// impl Solution4 {
+//     pub fn missing_number(nums: Vec<i32>) -> i32 {
+//         0
+//     }
+// }
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -37,5 +55,17 @@ mod tests {
         //     Solution2::missing_number(vec![9, 6, 4, 2, 3, 5, 7, 0, 1]),
         //     8
         // );
+
+        // assert_eq!(Solution3::missing_number(vec![3, 0, 1]), 2);
+        // assert_eq!(
+        //     Solution2::missing_number(vec![9, 6, 4, 2, 3, 5, 7, 0, 1]),
+        //     8
+        // );
+
+        // assert_eq!(Solution4::missing_number(vec![3, 0, 1]), 2);
+        // assert_eq!(
+        //     Solution2::missing_number(vec![9, 6, 4, 2, 3, 5, 7, 0, 1]),
+        //     8
+        // );
     }
 }

From 972cd52831025bc531bb600c38e31eb61dd5bbc8 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 17:24:18 +0800
Subject: [PATCH 16/82] add sol4

---
 kamyu104/src/missing_number.rs | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/kamyu104/src/missing_number.rs b/kamyu104/src/missing_number.rs
index cb9e37e..efac805 100644
--- a/kamyu104/src/missing_number.rs
+++ b/kamyu104/src/missing_number.rs
@@ -31,12 +31,12 @@ impl Solution1 {
 
 // Time:  O(n)
 // Space: O(1)
-// pub struct Solution4 {}
-// impl Solution4 {
-//     pub fn missing_number(nums: Vec<i32>) -> i32 {
-//         0
-//     }
-// }
+pub struct Solution4 {}
+impl Solution4 {
+    pub fn missing_number(nums: Vec<i32>) -> i32 {
+        ((0..nums.len() + 1).fold(0, |acc, i| acc + (i as i32))) - nums.iter().sum::<i32>()
+    }
+}
 
 #[cfg(test)]
 mod tests {
@@ -62,10 +62,10 @@ mod tests {
         //     8
         // );
 
-        // assert_eq!(Solution4::missing_number(vec![3, 0, 1]), 2);
-        // assert_eq!(
-        //     Solution2::missing_number(vec![9, 6, 4, 2, 3, 5, 7, 0, 1]),
-        //     8
-        // );
+        assert_eq!(Solution4::missing_number(vec![3, 0, 1]), 2);
+        assert_eq!(
+            Solution4::missing_number(vec![9, 6, 4, 2, 3, 5, 7, 0, 1]),
+            8
+        );
     }
 }

From 1baf60f84a799b64190164dab2e8013ac3e34b53 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 17:37:16 +0800
Subject: [PATCH 17/82] add sol3

---
 kamyu104/src/missing_number.rs | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/kamyu104/src/missing_number.rs b/kamyu104/src/missing_number.rs
index efac805..e12b6a5 100644
--- a/kamyu104/src/missing_number.rs
+++ b/kamyu104/src/missing_number.rs
@@ -22,12 +22,13 @@ impl Solution1 {
 
 // Time:  O(n)
 // Space: O(1)
-// pub struct Solution3 {}
-// impl Solution3 {
-//     pub fn missing_number(nums: Vec<i32>) -> i32 {
-//         0
-//     }
-// }
+pub struct Solution3 {}
+impl Solution3 {
+    pub fn missing_number(nums: Vec<i32>) -> i32 {
+        let len_xor = (0..nums.len() + 1).fold(0, |acc, i| acc ^ i as i32);
+        nums.iter().fold(len_xor, |acc, &i| acc ^ i)
+    }
+}
 
 // Time:  O(n)
 // Space: O(1)
@@ -56,11 +57,11 @@ mod tests {
         //     8
         // );
 
-        // assert_eq!(Solution3::missing_number(vec![3, 0, 1]), 2);
-        // assert_eq!(
-        //     Solution2::missing_number(vec![9, 6, 4, 2, 3, 5, 7, 0, 1]),
-        //     8
-        // );
+        assert_eq!(Solution3::missing_number(vec![3, 0, 1]), 2);
+        assert_eq!(
+            Solution3::missing_number(vec![9, 6, 4, 2, 3, 5, 7, 0, 1]),
+            8
+        );
 
         assert_eq!(Solution4::missing_number(vec![3, 0, 1]), 2);
         assert_eq!(

From db427603a84b1a8bfd4315d97e5ec4a93f20475b Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 17:39:56 +0800
Subject: [PATCH 18/82] udpate readme

---
 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 9a39431..1d738ce 100644
--- a/README.md
+++ b/README.md
@@ -55,10 +55,10 @@ cargo test
 0201 | [Bitwise AND of Numbers Range](https://leetcode.com/problems/bitwise-and-of-numbers-range/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/bitwise-and-of-numbers-range.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/bitwise-and-of-numbers-range.py) <br> [Rust](./kamyu104/src/bitwise_and_of_numbers_range.rs) | _O(1)_ | _O(1)_ | Medium ||
 0231 | [Power of Two](https://leetcode.com/problems/power-of-two/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/power-of-two.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/power-of-two.py) <br> [Rust](./kamyu104/src/power_of_two.rs) | _O(1)_ | _O(1)_ | Easy | LintCode |
 0260 | [Single Number III](https://leetcode.com/problems/single-number-iii/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/single-number-iii.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/single-number-iii.py) <br> [Rust](./kamyu104/src/single_number_iii.rs) | _O(n)_ | _O(1)_          | Medium         ||
+0268| [Missing Number](https://leetcode.com/problems/missing-number/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/missing-number.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/missing-number.py) <br> [Rust](./kamyu104/src/missing_number.rs) | _O(n)_ |  _O(1)_ | Medium         | LintCode ||
 
 <!-- 
 
-0268| [Missing Number](https://leetcode.com/problems/missing-number/) | [C++](./C++/missing-number.cpp) [Python](./Python/missing-number.py)  | _O(n)_ |  _O(1)_ | Medium         | LintCode ||
 0318| [Maximum Product of Word Lengths](https://leetcode.com/problems/maximum-product-of-word-lengths/) | [C++](./C++/maximum-product-of-word-lengths.cpp) [Python](./Python/maximum-product-of-word-lengths.py)  | _O(n)_ ~ _O(n^2)_ |  _O(n)_ | Medium         || Bit Manipulation, Counting Sort, Pruning|
 0342 | [Power of Four](https://leetcode.com/problems/power-of-four/) | [C++](./C++/power-of-four.cpp) [Python](./Python/power-of-four.py) | _O(1)_ | _O(1)_ | Easy | |
 0371 | [Sum of Two Integers](https://leetcode.com/problems/sum-of-two-integers/) | [C++](./C++/sum-of-two-integers.cpp) [Python](./Python/sum-of-two-integers.py) | _O(1)_ | _O(1)_ | Easy | LintCode |

From e7ea8027409df2ef6054a5aa28c6c90f90079951 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 17:59:19 +0800
Subject: [PATCH 19/82] init maximum_product_of_word_lengths

---
 kamyu104/src/main.rs                            | 1 +
 kamyu104/src/maximum_product_of_word_lengths.rs | 0
 2 files changed, 1 insertion(+)
 create mode 100644 kamyu104/src/maximum_product_of_word_lengths.rs

diff --git a/kamyu104/src/main.rs b/kamyu104/src/main.rs
index 855a106..e821b08 100644
--- a/kamyu104/src/main.rs
+++ b/kamyu104/src/main.rs
@@ -6,4 +6,5 @@ mod reverse_bits;
 mod single_number;
 mod single_number_ii;
 mod single_number_iii;
+mod maximum_product_of_word_lengths;
 mod template;
diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
new file mode 100644
index 0000000..e69de29

From 6c30f646736d8ff6fbf305dfce5505469e07a586 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 18:01:46 +0800
Subject: [PATCH 20/82] update readme

---
 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 1d738ce..638d60c 100644
--- a/README.md
+++ b/README.md
@@ -56,10 +56,10 @@ cargo test
 0231 | [Power of Two](https://leetcode.com/problems/power-of-two/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/power-of-two.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/power-of-two.py) <br> [Rust](./kamyu104/src/power_of_two.rs) | _O(1)_ | _O(1)_ | Easy | LintCode |
 0260 | [Single Number III](https://leetcode.com/problems/single-number-iii/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/single-number-iii.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/single-number-iii.py) <br> [Rust](./kamyu104/src/single_number_iii.rs) | _O(n)_ | _O(1)_          | Medium         ||
 0268| [Missing Number](https://leetcode.com/problems/missing-number/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/missing-number.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/missing-number.py) <br> [Rust](./kamyu104/src/missing_number.rs) | _O(n)_ |  _O(1)_ | Medium         | LintCode ||
+0318| [Maximum Product of Word Lengths](https://leetcode.com/problems/maximum-product-of-word-lengths/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/maximum-product-of-word-lengths.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-product-of-word-lengths.py) <br> [Rust](./kamyu104/src/maximum_product_of_word_lengths.rs) | _O(n)_ ~ _O(n^2)_ |  _O(n)_ | Medium         || Bit Manipulation, Counting Sort, Pruning|
 
 <!-- 
 
-0318| [Maximum Product of Word Lengths](https://leetcode.com/problems/maximum-product-of-word-lengths/) | [C++](./C++/maximum-product-of-word-lengths.cpp) [Python](./Python/maximum-product-of-word-lengths.py)  | _O(n)_ ~ _O(n^2)_ |  _O(n)_ | Medium         || Bit Manipulation, Counting Sort, Pruning|
 0342 | [Power of Four](https://leetcode.com/problems/power-of-four/) | [C++](./C++/power-of-four.cpp) [Python](./Python/power-of-four.py) | _O(1)_ | _O(1)_ | Easy | |
 0371 | [Sum of Two Integers](https://leetcode.com/problems/sum-of-two-integers/) | [C++](./C++/sum-of-two-integers.cpp) [Python](./Python/sum-of-two-integers.py) | _O(1)_ | _O(1)_ | Easy | LintCode |
 0389 | [Find the Difference](https://leetcode.com/problems/find-the-difference/) | [C++](./C++/find-the-difference.cpp) [Python](./Python/find-the-difference.py) | _O(n)_ | _O(1)_ | Easy | |

From 987dcda1ed5e3c9ea158e981406ed7ce2c4e8cd8 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 18:05:04 +0800
Subject: [PATCH 21/82] minor

---
 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 638d60c..3ae0bc5 100644
--- a/README.md
+++ b/README.md
@@ -56,7 +56,7 @@ cargo test
 0231 | [Power of Two](https://leetcode.com/problems/power-of-two/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/power-of-two.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/power-of-two.py) <br> [Rust](./kamyu104/src/power_of_two.rs) | _O(1)_ | _O(1)_ | Easy | LintCode |
 0260 | [Single Number III](https://leetcode.com/problems/single-number-iii/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/single-number-iii.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/single-number-iii.py) <br> [Rust](./kamyu104/src/single_number_iii.rs) | _O(n)_ | _O(1)_          | Medium         ||
 0268| [Missing Number](https://leetcode.com/problems/missing-number/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/missing-number.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/missing-number.py) <br> [Rust](./kamyu104/src/missing_number.rs) | _O(n)_ |  _O(1)_ | Medium         | LintCode ||
-0318| [Maximum Product of Word Lengths](https://leetcode.com/problems/maximum-product-of-word-lengths/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/maximum-product-of-word-lengths.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-product-of-word-lengths.py) <br> [Rust](./kamyu104/src/maximum_product_of_word_lengths.rs) | _O(n)_ ~ _O(n^2)_ |  _O(n)_ | Medium         || Bit Manipulation, Counting Sort, Pruning|
+0318| [Maximum Product of Word Lengths](https://leetcode.com/problems/maximum-product-of-word-lengths/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/maximum-product-of-word-lengths.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-product-of-word-lengths.py) <br> [Rust](./kamyu104/src/maximum_product_of_word_lengths.rs) | _O(n)_ ~ _O(n^2)_ |  _O(n)_ | Medium         || Bit Manipulation, Counting Sort, Pruning|
 
 <!-- 
 

From b1a1712b755c5a89ea424be2d922a35938210360 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 18:07:32 +0800
Subject: [PATCH 22/82] update

---
 README.md                                      | 18 +++++++++---------
 .../src/maximum_product_of_word_lengths.rs     | 16 ++++++++++++++++
 2 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/README.md b/README.md
index 3ae0bc5..255b2d2 100644
--- a/README.md
+++ b/README.md
@@ -48,15 +48,15 @@ cargo test
 #### Bit Manipulation
 |  #  | Title           |  Solution       |  Time           | Space           | Difficulty    | Tag          | Note| 
 |-----|---------------- | --------------- | --------------- | --------------- | ------------- |--------------|-----|
-0136 | [Single Number](https://leetcode.com/problems/single-number/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/single-number.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/single-number.py) <br> [Rust](./kamyu104/src/single_number.rs) | _O(n)_       | _O(1)_          | Easy         |||
-0137 | [Single Number II](https://leetcode.com/problems/single-number-ii/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/single-number-ii.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/single-number-ii.py) <br> [Rust](./kamyu104/src/single_number_ii.rs) | _O(n)_ | _O(1)_          | Medium         |||
-0190 | [Reverse Bits](https://leetcode.com/problems/reverse-bits/)  | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/reverse-bits.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/reverse-bits.py) <br> [Rust](./kamyu104/src/reverse_bits.rs) | _O(1)_        | _O(1)_          | Easy           |||
-0191  |[Number of 1 Bits](https://leetcode.com/problems/number-of-1-bits/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/number-of-1-bits.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/number-of-1-bits.py) <br> [Rust](./kamyu104/src/number_of_1_bits.rs) | _O(1)_ | _O(1)_          | Easy           |||
-0201 | [Bitwise AND of Numbers Range](https://leetcode.com/problems/bitwise-and-of-numbers-range/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/bitwise-and-of-numbers-range.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/bitwise-and-of-numbers-range.py) <br> [Rust](./kamyu104/src/bitwise_and_of_numbers_range.rs) | _O(1)_ | _O(1)_ | Medium ||
-0231 | [Power of Two](https://leetcode.com/problems/power-of-two/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/power-of-two.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/power-of-two.py) <br> [Rust](./kamyu104/src/power_of_two.rs) | _O(1)_ | _O(1)_ | Easy | LintCode |
-0260 | [Single Number III](https://leetcode.com/problems/single-number-iii/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/single-number-iii.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/single-number-iii.py) <br> [Rust](./kamyu104/src/single_number_iii.rs) | _O(n)_ | _O(1)_          | Medium         ||
-0268| [Missing Number](https://leetcode.com/problems/missing-number/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/missing-number.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/missing-number.py) <br> [Rust](./kamyu104/src/missing_number.rs) | _O(n)_ |  _O(1)_ | Medium         | LintCode ||
-0318| [Maximum Product of Word Lengths](https://leetcode.com/problems/maximum-product-of-word-lengths/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/maximum-product-of-word-lengths.cpp), [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-product-of-word-lengths.py) <br> [Rust](./kamyu104/src/maximum_product_of_word_lengths.rs) | _O(n)_ ~ _O(n^2)_ |  _O(n)_ | Medium         || Bit Manipulation, Counting Sort, Pruning|
+0136 | [Single Number](https://leetcode.com/problems/single-number/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/single-number.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/single-number.py) <br> [Rust](./kamyu104/src/single_number.rs) | _O(n)_       | _O(1)_          | Easy         |||
+0137 | [Single Number II](https://leetcode.com/problems/single-number-ii/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/single-number-ii.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/single-number-ii.py) <br> [Rust](./kamyu104/src/single_number_ii.rs) | _O(n)_ | _O(1)_          | Medium         |||
+0190 | [Reverse Bits](https://leetcode.com/problems/reverse-bits/)  | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/reverse-bits.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/reverse-bits.py) <br> [Rust](./kamyu104/src/reverse_bits.rs) | _O(1)_        | _O(1)_          | Easy           |||
+0191  |[Number of 1 Bits](https://leetcode.com/problems/number-of-1-bits/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/number-of-1-bits.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/number-of-1-bits.py) <br> [Rust](./kamyu104/src/number_of_1_bits.rs) | _O(1)_ | _O(1)_          | Easy           |||
+0201 | [Bitwise AND of Numbers Range](https://leetcode.com/problems/bitwise-and-of-numbers-range/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/bitwise-and-of-numbers-range.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/bitwise-and-of-numbers-range.py) <br> [Rust](./kamyu104/src/bitwise_and_of_numbers_range.rs) | _O(1)_ | _O(1)_ | Medium ||
+0231 | [Power of Two](https://leetcode.com/problems/power-of-two/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/power-of-two.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/power-of-two.py) <br> [Rust](./kamyu104/src/power_of_two.rs) | _O(1)_ | _O(1)_ | Easy | LintCode |
+0260 | [Single Number III](https://leetcode.com/problems/single-number-iii/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/single-number-iii.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/single-number-iii.py) <br> [Rust](./kamyu104/src/single_number_iii.rs) | _O(n)_ | _O(1)_          | Medium         ||
+0268| [Missing Number](https://leetcode.com/problems/missing-number/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/missing-number.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/missing-number.py) <br> [Rust](./kamyu104/src/missing_number.rs) | _O(n)_ |  _O(1)_ | Medium         | LintCode ||
+0318| [Maximum Product of Word Lengths](https://leetcode.com/problems/maximum-product-of-word-lengths/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/maximum-product-of-word-lengths.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-product-of-word-lengths.py) <br> [Rust](./kamyu104/src/maximum_product_of_word_lengths.rs) | _O(n)_ ~ _O(n^2)_ |  _O(n)_ | Medium         || Bit Manipulation, Counting Sort, Pruning|
 
 <!-- 
 
diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index e69de29..3d67639 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -0,0 +1,16 @@
+pub struct Solution {}
+impl Solution {
+    pub fn max_product(words: Vec<String>) -> i32 {
+        0
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    // Note this useful idiom: importing names from outer (for mod tests) scope.
+    use super::*;
+
+    #[test]
+    fn test_max_product() {
+    }
+}

From be4bafb68e931b2dd967f3267fe58d0dc4d10847 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 18:09:49 +0800
Subject: [PATCH 23/82] fix readme

---
 README.md | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/README.md b/README.md
index 255b2d2..ee4678e 100644
--- a/README.md
+++ b/README.md
@@ -48,15 +48,15 @@ cargo test
 #### Bit Manipulation
 |  #  | Title           |  Solution       |  Time           | Space           | Difficulty    | Tag          | Note| 
 |-----|---------------- | --------------- | --------------- | --------------- | ------------- |--------------|-----|
-0136 | [Single Number](https://leetcode.com/problems/single-number/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/single-number.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/single-number.py) <br> [Rust](./kamyu104/src/single_number.rs) | _O(n)_       | _O(1)_          | Easy         |||
-0137 | [Single Number II](https://leetcode.com/problems/single-number-ii/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/single-number-ii.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/single-number-ii.py) <br> [Rust](./kamyu104/src/single_number_ii.rs) | _O(n)_ | _O(1)_          | Medium         |||
-0190 | [Reverse Bits](https://leetcode.com/problems/reverse-bits/)  | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/reverse-bits.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/reverse-bits.py) <br> [Rust](./kamyu104/src/reverse_bits.rs) | _O(1)_        | _O(1)_          | Easy           |||
-0191  |[Number of 1 Bits](https://leetcode.com/problems/number-of-1-bits/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/number-of-1-bits.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/number-of-1-bits.py) <br> [Rust](./kamyu104/src/number_of_1_bits.rs) | _O(1)_ | _O(1)_          | Easy           |||
-0201 | [Bitwise AND of Numbers Range](https://leetcode.com/problems/bitwise-and-of-numbers-range/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/bitwise-and-of-numbers-range.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/bitwise-and-of-numbers-range.py) <br> [Rust](./kamyu104/src/bitwise_and_of_numbers_range.rs) | _O(1)_ | _O(1)_ | Medium ||
-0231 | [Power of Two](https://leetcode.com/problems/power-of-two/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/power-of-two.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/power-of-two.py) <br> [Rust](./kamyu104/src/power_of_two.rs) | _O(1)_ | _O(1)_ | Easy | LintCode |
-0260 | [Single Number III](https://leetcode.com/problems/single-number-iii/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/single-number-iii.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/single-number-iii.py) <br> [Rust](./kamyu104/src/single_number_iii.rs) | _O(n)_ | _O(1)_          | Medium         ||
-0268| [Missing Number](https://leetcode.com/problems/missing-number/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/missing-number.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/missing-number.py) <br> [Rust](./kamyu104/src/missing_number.rs) | _O(n)_ |  _O(1)_ | Medium         | LintCode ||
-0318| [Maximum Product of Word Lengths](https://leetcode.com/problems/maximum-product-of-word-lengths/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/maximum-product-of-word-lengths.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-product-of-word-lengths.py) <br> [Rust](./kamyu104/src/maximum_product_of_word_lengths.rs) | _O(n)_ ~ _O(n^2)_ |  _O(n)_ | Medium         || Bit Manipulation, Counting Sort, Pruning|
+0136 | [Single Number](https://leetcode.com/problems/single-number/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/single-number.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/single-number.py) <br>------</br> [Rust](./kamyu104/src/single_number.rs) | _O(n)_       | _O(1)_          | Easy         |||
+0137 | [Single Number II](https://leetcode.com/problems/single-number-ii/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/single-number-ii.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/single-number-ii.py) <br>------</br> [Rust](./kamyu104/src/single_number_ii.rs) | _O(n)_ | _O(1)_          | Medium         |||
+0190 | [Reverse Bits](https://leetcode.com/problems/reverse-bits/)  | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/reverse-bits.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/reverse-bits.py) <br>------</br> [Rust](./kamyu104/src/reverse_bits.rs) | _O(1)_        | _O(1)_          | Easy           |||
+0191  |[Number of 1 Bits](https://leetcode.com/problems/number-of-1-bits/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/number-of-1-bits.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/number-of-1-bits.py) <br>------</br> [Rust](./kamyu104/src/number_of_1_bits.rs) | _O(1)_ | _O(1)_          | Easy           |||
+0201 | [Bitwise AND of Numbers Range](https://leetcode.com/problems/bitwise-and-of-numbers-range/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/bitwise-and-of-numbers-range.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/bitwise-and-of-numbers-range.py) <br>------</br> [Rust](./kamyu104/src/bitwise_and_of_numbers_range.rs) | _O(1)_ | _O(1)_ | Medium ||
+0231 | [Power of Two](https://leetcode.com/problems/power-of-two/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/power-of-two.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/power-of-two.py) <br>------</br> [Rust](./kamyu104/src/power_of_two.rs) | _O(1)_ | _O(1)_ | Easy | LintCode |
+0260 | [Single Number III](https://leetcode.com/problems/single-number-iii/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/single-number-iii.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/single-number-iii.py) <br>------</br> [Rust](./kamyu104/src/single_number_iii.rs) | _O(n)_ | _O(1)_          | Medium         ||
+0268| [Missing Number](https://leetcode.com/problems/missing-number/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/missing-number.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/missing-number.py) <br>------</br> [Rust](./kamyu104/src/missing_number.rs) | _O(n)_ |  _O(1)_ | Medium         | LintCode ||
+0318| [Maximum Product of Word Lengths](https://leetcode.com/problems/maximum-product-of-word-lengths/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/maximum-product-of-word-lengths.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-product-of-word-lengths.py) <br>------</br> [Rust](./kamyu104/src/maximum_product_of_word_lengths.rs) | _O(n)_ ~ _O(n^2)_ |  _O(n)_ | Medium         || Bit Manipulation, Counting Sort, Pruning|
 
 <!-- 
 

From eb63411ddb479032fb7dd944220f52db5ba441f7 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 18:14:38 +0800
Subject: [PATCH 24/82] init max_product

---
 kamyu104/src/maximum_product_of_word_lengths.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index 3d67639..9d86c2a 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -7,10 +7,12 @@ impl Solution {
 
 #[cfg(test)]
 mod tests {
-    // Note this useful idiom: importing names from outer (for mod tests) scope.
     use super::*;
 
     #[test]
     fn test_max_product() {
+        assert_max_product!(Solution::max_product(vec!["abcw","baz","foo","bar","xtfn","abcdef"]), 16);
+        assert_max_product!(Solution::max_product(vec!["a","ab","abc","d","cd","bcd","abcd"]), 4);
+        assert_max_product!(Solution::max_product(vec!["a","aa","aaa","aaaa"]), 0);
     }
 }

From 21fd9ba0130a35a2242619d321dfaef33bb5ac00 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Sat, 20 Jul 2019 18:19:57 +0800
Subject: [PATCH 25/82] update

---
 kamyu104/src/main.rs                            | 2 +-
 kamyu104/src/maximum_product_of_word_lengths.rs | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/kamyu104/src/main.rs b/kamyu104/src/main.rs
index e821b08..5c1a2ae 100644
--- a/kamyu104/src/main.rs
+++ b/kamyu104/src/main.rs
@@ -1,4 +1,5 @@
 mod bitwise_and_of_numbers_range;
+mod maximum_product_of_word_lengths;
 mod missing_number;
 mod number_of_1_bits;
 mod power_of_two;
@@ -6,5 +7,4 @@ mod reverse_bits;
 mod single_number;
 mod single_number_ii;
 mod single_number_iii;
-mod maximum_product_of_word_lengths;
 mod template;
diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index 9d86c2a..e4890b0 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -11,8 +11,8 @@ mod tests {
 
     #[test]
     fn test_max_product() {
-        assert_max_product!(Solution::max_product(vec!["abcw","baz","foo","bar","xtfn","abcdef"]), 16);
-        assert_max_product!(Solution::max_product(vec!["a","ab","abc","d","cd","bcd","abcd"]), 4);
-        assert_max_product!(Solution::max_product(vec!["a","aa","aaa","aaaa"]), 0);
+        // assert_max_product!(Solution::max_product(vec!["abcw","baz","foo","bar","xtfn","abcdef"]), 16);
+        // assert_max_product!(Solution::max_product(vec!["a","ab","abc","d","cd","bcd","abcd"]), 4);
+        // assert_max_product!(Solution::max_product(vec!["a","aa","aaa","aaaa"]), 0);
     }
 }

From 7235506aa88dc498d7318809930d64be42d08487 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Tue, 23 Jul 2019 09:01:39 +0800
Subject: [PATCH 26/82] wip

---
 .../src/maximum_product_of_word_lengths.rs     | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index e4890b0..96d0f64 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -1,5 +1,19 @@
-pub struct Solution {}
-impl Solution {
+// Time:  O(n) ~ O(n^2)
+// Space: O(n)
+// Counting Sort + Pruning + Bit Manipulation
+pub struct Solution1 {}
+impl Solution1 {
+    pub fn max_product(words: Vec<String>) -> i32 {
+        0
+    }
+}
+
+
+// Time:  O(nlogn) ~ O(n^2)
+// Space: O(n)
+// Sorting + Pruning + Bit Manipulation
+pub struct Solution2 {}
+impl Solution2 {
     pub fn max_product(words: Vec<String>) -> i32 {
         0
     }

From 78390b489371077153484b35e77f84d3f367cbce Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Tue, 23 Jul 2019 09:20:43 +0800
Subject: [PATCH 27/82] from &str

---
 kamyu104/src/maximum_product_of_word_lengths.rs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index 96d0f64..f673197 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -21,12 +21,12 @@ impl Solution2 {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
+    use super::*;    
 
     #[test]
     fn test_max_product() {
-        // assert_max_product!(Solution::max_product(vec!["abcw","baz","foo","bar","xtfn","abcdef"]), 16);
-        // assert_max_product!(Solution::max_product(vec!["a","ab","abc","d","cd","bcd","abcd"]), 4);
-        // assert_max_product!(Solution::max_product(vec!["a","aa","aaa","aaaa"]), 0);
+        // assert_eq!(Solution1::max_product(vec!["abcw","baz","foo","bar","xtfn","abcdef"].iter().map(|&x| String::from(x)).collect()), 16);
+        // assert_eq!(Solution1::max_product(vec!["a","ab","abc","d","cd","bcd","abcd"].iter().map(|&x| String::from(x)).collect()), 4);
+        // assert_eq!(Solution::max_product(vec!["a","aa","aaa","aaaa"].iter().map(|&x| String::from(x)).collect()), 0);
     }
 }

From bcdaf0dc53ea696ce005f3ee28e4e1e760e02736 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Tue, 23 Jul 2019 09:31:07 +0800
Subject: [PATCH 28/82] minor

---
 kamyu104/src/maximum_product_of_word_lengths.rs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index f673197..25137eb 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -15,6 +15,8 @@ impl Solution1 {
 pub struct Solution2 {}
 impl Solution2 {
     pub fn max_product(words: Vec<String>) -> i32 {
+        let mut ws = words.clone();
+        ws.sort_by(|a, b| a.len().cmp(&b.len()));
         0
     }
 }
@@ -27,6 +29,10 @@ mod tests {
     fn test_max_product() {
         // assert_eq!(Solution1::max_product(vec!["abcw","baz","foo","bar","xtfn","abcdef"].iter().map(|&x| String::from(x)).collect()), 16);
         // assert_eq!(Solution1::max_product(vec!["a","ab","abc","d","cd","bcd","abcd"].iter().map(|&x| String::from(x)).collect()), 4);
-        // assert_eq!(Solution::max_product(vec!["a","aa","aaa","aaaa"].iter().map(|&x| String::from(x)).collect()), 0);
+        // assert_eq!(Solution1::max_product(vec!["a","aa","aaa","aaaa"].iter().map(|&x| String::from(x)).collect()), 0);
+
+        // assert_eq!(Solution2::max_product(vec!["abcw","baz","foo","bar","xtfn","abcdef"].iter().map(|&x| String::from(x)).collect()), 16);
+        // assert_eq!(Solution2::max_product(vec!["a","ab","abc","d","cd","bcd","abcd"].iter().map(|&x| String::from(x)).collect()), 4);
+        // assert_eq!(Solution2::max_product(vec!["a","aa","aaa","aaaa"].iter().map(|&x| String::from(x)).collect()), 0);
     }
 }

From ddad596789e50a0166bdab91159f33b7e3f16af6 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Tue, 23 Jul 2019 09:40:45 +0800
Subject: [PATCH 29/82] imnor

---
 kamyu104/src/maximum_product_of_word_lengths.rs | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index 25137eb..d309b7c 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -15,8 +15,7 @@ impl Solution1 {
 pub struct Solution2 {}
 impl Solution2 {
     pub fn max_product(words: Vec<String>) -> i32 {
-        let mut ws = words.clone();
-        ws.sort_by(|a, b| a.len().cmp(&b.len()));
+        let mut sorted_words = words.clone().sort_by(|a, b| a.len().cmp(&b.len()));
         0
     }
 }

From f9def884eeb4e225696c95e4ae3c50294b9b8f3f Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Tue, 23 Jul 2019 14:25:15 +0800
Subject: [PATCH 30/82] minor

---
 kamyu104/src/maximum_product_of_word_lengths.rs | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index d309b7c..b8fee7e 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -8,7 +8,6 @@ impl Solution1 {
     }
 }
 
-
 // Time:  O(nlogn) ~ O(n^2)
 // Space: O(n)
 // Sorting + Pruning + Bit Manipulation
@@ -16,13 +15,20 @@ pub struct Solution2 {}
 impl Solution2 {
     pub fn max_product(words: Vec<String>) -> i32 {
         let mut sorted_words = words.clone().sort_by(|a, b| a.len().cmp(&b.len()));
+        // vector<int> bits(words.size());
+        let bits: Vec<i32> = vec![0; words.len()];
+        // for (int i = 0; i < words.size(); ++i) {
+        //     for (const auto& c : words[i]) {
+        //         bits[i] |= (1 << (c - 'a'));
+        //     }
+        // }
         0
     }
 }
 
 #[cfg(test)]
 mod tests {
-    use super::*;    
+    use super::*;
 
     #[test]
     fn test_max_product() {

From e84f3b784aaf09cc25de36e6fe1b0ed76f2290d8 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Tue, 23 Jul 2019 14:29:37 +0800
Subject: [PATCH 31/82] wip

---
 kamyu104/src/maximum_product_of_word_lengths.rs | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index b8fee7e..83ffe85 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -15,14 +15,21 @@ pub struct Solution2 {}
 impl Solution2 {
     pub fn max_product(words: Vec<String>) -> i32 {
         let mut sorted_words = words.clone().sort_by(|a, b| a.len().cmp(&b.len()));
-        // vector<int> bits(words.size());
         let bits: Vec<i32> = vec![0; words.len()];
-        // for (int i = 0; i < words.size(); ++i) {
-        //     for (const auto& c : words[i]) {
-        //         bits[i] |= (1 << (c - 'a'));
+        // for i in 0..words.len(){
+        //     for c in words[i].chars(){
+        //         bits[i] |= (1 << (c - 'a'))
         //     }
         // }
-        0
+        let max_product :i32 = 0;
+        // for (int i = 0; i + 1 < words.size() && pow(words[i].length(), 2) > max_product; ++i) {
+        //     for (int j = i + 1; j < words.size() && words[i].length() * words[j].length() > max_product; ++j) {
+        //         if (!(bits[i] & bits[j])) {
+        //             max_product = words[i].length() * words[j].length();
+        //         }
+        //     }
+        // }
+        max_product
     }
 }
 

From 004780b763379b713706dcbcfc3caf35a849682c Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Tue, 23 Jul 2019 17:13:18 +0800
Subject: [PATCH 32/82] minor

---
 kamyu104/src/maximum_product_of_word_lengths.rs | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index 83ffe85..ddebf86 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -15,12 +15,12 @@ pub struct Solution2 {}
 impl Solution2 {
     pub fn max_product(words: Vec<String>) -> i32 {
         let mut sorted_words = words.clone().sort_by(|a, b| a.len().cmp(&b.len()));
-        let bits: Vec<i32> = vec![0; words.len()];
-        // for i in 0..words.len(){
-        //     for c in words[i].chars(){
-        //         bits[i] |= (1 << (c - 'a'))
-        //     }
-        // }
+        let mut bits: Vec<i32> = vec![0; words.len()];
+        for i in 0..words.len(){
+            for c in words[i].chars(){
+                bits[i] |= (1 << (c as u32 - 'a' as u32))
+            }
+        }
         let max_product :i32 = 0;
         // for (int i = 0; i + 1 < words.size() && pow(words[i].length(), 2) > max_product; ++i) {
         //     for (int j = i + 1; j < words.size() && words[i].length() * words[j].length() > max_product; ++j) {

From 14cd70f95fe644f0afd4e90879cb50bd3db4df2a Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Tue, 23 Jul 2019 17:26:43 +0800
Subject: [PATCH 33/82] fix

---
 kamyu104/src/maximum_product_of_word_lengths.rs | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index ddebf86..74ad23a 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -14,10 +14,11 @@ impl Solution1 {
 pub struct Solution2 {}
 impl Solution2 {
     pub fn max_product(words: Vec<String>) -> i32 {
-        let mut sorted_words = words.clone().sort_by(|a, b| a.len().cmp(&b.len()));
+        let mut sorted_words = words.clone();
+        sorted_words.sort_by(|a, b| a.len().cmp(&b.len()));
         let mut bits: Vec<i32> = vec![0; words.len()];
-        for i in 0..words.len(){
-            for c in words[i].chars(){
+        for i in 0..sorted_words.len(){
+            for c in sorted_words[i].chars(){
                 bits[i] |= (1 << (c as u32 - 'a' as u32))
             }
         }

From 81ea210f2b29bca6f6756c9ca03c2dcc803e1f75 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Tue, 23 Jul 2019 18:39:21 +0800
Subject: [PATCH 34/82] ???

---
 .../src/maximum_product_of_word_lengths.rs    | 59 ++++++++++++++-----
 1 file changed, 45 insertions(+), 14 deletions(-)

diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index 74ad23a..736c9f2 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -17,19 +17,26 @@ impl Solution2 {
         let mut sorted_words = words.clone();
         sorted_words.sort_by(|a, b| a.len().cmp(&b.len()));
         let mut bits: Vec<i32> = vec![0; words.len()];
-        for i in 0..sorted_words.len(){
-            for c in sorted_words[i].chars(){
-                bits[i] |= (1 << (c as u32 - 'a' as u32))
+        for i in 0..sorted_words.len() {
+            for c in sorted_words[i].chars() {
+                bits[i] |= 1 << (c as u32 - 'a' as u32);
             }
         }
-        let max_product :i32 = 0;
-        // for (int i = 0; i + 1 < words.size() && pow(words[i].length(), 2) > max_product; ++i) {
-        //     for (int j = i + 1; j < words.size() && words[i].length() * words[j].length() > max_product; ++j) {
-        //         if (!(bits[i] & bits[j])) {
-        //             max_product = words[i].length() * words[j].length();
-        //         }
-        //     }
-        // }
+        let mut max_product: i32 = 0;
+        let mut i: usize = 0;
+        while i + 1 < sorted_words.len() && sorted_words[i].len().pow(2) as i32 > max_product {
+            let mut j: usize = i + 1;
+            while j < sorted_words.len()
+                && (sorted_words[i].len() * sorted_words[j].len()) as i32 > max_product
+            {
+                if bits[i] & bits[j] == 0 {
+                    max_product = (sorted_words[i].len() * sorted_words[j].len()) as i32;
+                }
+                j += 1;
+            }
+
+            i += 1;
+        }
         max_product
     }
 }
@@ -40,9 +47,33 @@ mod tests {
 
     #[test]
     fn test_max_product() {
-        // assert_eq!(Solution1::max_product(vec!["abcw","baz","foo","bar","xtfn","abcdef"].iter().map(|&x| String::from(x)).collect()), 16);
-        // assert_eq!(Solution1::max_product(vec!["a","ab","abc","d","cd","bcd","abcd"].iter().map(|&x| String::from(x)).collect()), 4);
-        // assert_eq!(Solution1::max_product(vec!["a","aa","aaa","aaaa"].iter().map(|&x| String::from(x)).collect()), 0);
+        assert_eq!(
+            Solution2::max_product(
+                vec!["abcw", "baz", "foo", "bar", "xtfn", "abcdef"]
+                    .iter()
+                    .map(|&x| String::from(x))
+                    .collect()
+            ),
+            16
+        );
+        assert_eq!(
+            Solution2::max_product(
+                vec!["a", "ab", "abc", "d", "cd", "bcd", "abcd"]
+                    .iter()
+                    .map(|&x| String::from(x))
+                    .collect()
+            ),
+            4
+        );
+        assert_eq!(
+            Solution2::max_product(
+                vec!["a", "aa", "aaa", "aaaa"]
+                    .iter()
+                    .map(|&x| String::from(x))
+                    .collect()
+            ),
+            0
+        );
 
         // assert_eq!(Solution2::max_product(vec!["abcw","baz","foo","bar","xtfn","abcdef"].iter().map(|&x| String::from(x)).collect()), 16);
         // assert_eq!(Solution2::max_product(vec!["a","ab","abc","d","cd","bcd","abcd"].iter().map(|&x| String::from(x)).collect()), 4);

From 203a2bbb0279d4ef697ea12169a1363c2872cdf5 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Tue, 23 Jul 2019 18:42:02 +0800
Subject: [PATCH 35/82] fix

---
 kamyu104/src/maximum_product_of_word_lengths.rs | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index 736c9f2..8000a1e 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -15,7 +15,7 @@ pub struct Solution2 {}
 impl Solution2 {
     pub fn max_product(words: Vec<String>) -> i32 {
         let mut sorted_words = words.clone();
-        sorted_words.sort_by(|a, b| a.len().cmp(&b.len()));
+        sorted_words.sort_by(|a, b| b.len().cmp(&a.len()));
         let mut bits: Vec<i32> = vec![0; words.len()];
         for i in 0..sorted_words.len() {
             for c in sorted_words[i].chars() {
@@ -34,7 +34,6 @@ impl Solution2 {
                 }
                 j += 1;
             }
-
             i += 1;
         }
         max_product
@@ -74,9 +73,5 @@ mod tests {
             ),
             0
         );
-
-        // assert_eq!(Solution2::max_product(vec!["abcw","baz","foo","bar","xtfn","abcdef"].iter().map(|&x| String::from(x)).collect()), 16);
-        // assert_eq!(Solution2::max_product(vec!["a","ab","abc","d","cd","bcd","abcd"].iter().map(|&x| String::from(x)).collect()), 4);
-        // assert_eq!(Solution2::max_product(vec!["a","aa","aaa","aaaa"].iter().map(|&x| String::from(x)).collect()), 0);
     }
 }

From b47565007873ab8975671c148f0223ffd753298f Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 24 Jul 2019 07:44:30 +0800
Subject: [PATCH 36/82] add

---
 kamyu104/src/maximum_product_of_word_lengths.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index 8000a1e..1031054 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -75,3 +75,13 @@ mod tests {
         );
     }
 }
+
+
+// TODO: use macro
+/*
+macro_rules! s {
+    ($v:ty) => (
+        $v.to_string()
+    )
+}
+*/
\ No newline at end of file

From 451b9edee0f5948964f0c6824d2934adac672bb9 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 24 Jul 2019 07:57:20 +0800
Subject: [PATCH 37/82] update

---
 kamyu104/src/maximum_product_of_word_lengths.rs | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index 1031054..ee68205 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -74,14 +74,4 @@ mod tests {
             0
         );
     }
-}
-
-
-// TODO: use macro
-/*
-macro_rules! s {
-    ($v:ty) => (
-        $v.to_string()
-    )
-}
-*/
\ No newline at end of file
+}
\ No newline at end of file

From 8322ca4287d50e29b8a619924e6698ff5dbb4f3e Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 24 Jul 2019 08:01:49 +0800
Subject: [PATCH 38/82] clean

---
 .../src/maximum_product_of_word_lengths.rs    | 23 +++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index ee68205..ef557d9 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -1,6 +1,7 @@
 // Time:  O(n) ~ O(n^2)
 // Space: O(n)
 // Counting Sort + Pruning + Bit Manipulation
+// https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/maximum-product-of-word-lengths.cpp#L1-L40
 pub struct Solution1 {}
 impl Solution1 {
     pub fn max_product(words: Vec<String>) -> i32 {
@@ -40,6 +41,28 @@ impl Solution2 {
     }
 }
 
+
+// # Time:  O(n) ~ O(n^2)
+// # Space: O(n)
+// https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-product-of-word-lengths.py#L1-L36
+pub struct Solution3 {}
+impl Solution3 {
+    pub fn max_product(words: Vec<String>) -> i32 {
+        0
+    }
+}
+
+// # Time:  O(nlogn) ~ O(n^2)
+// # Space: O(n)
+// # Sorting + Pruning + Bit Manipulation
+// https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-product-of-word-lengths.py#L38-L62
+pub struct Solution4 {}
+impl Solution4 {
+    pub fn max_product(words: Vec<String>) -> i32 {
+        0
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

From cf3c97a95fb11ed51e1e33c78976cd0c8b4eda63 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 24 Jul 2019 08:23:15 +0800
Subject: [PATCH 39/82] fix

---
 README.md                                     | 12 +++----
 .../src/maximum_product_of_word_lengths.rs    | 36 +++++++++----------
 2 files changed, 24 insertions(+), 24 deletions(-)

diff --git a/README.md b/README.md
index ee4678e..977981a 100644
--- a/README.md
+++ b/README.md
@@ -3,6 +3,12 @@
 [![Build Status](https://travis-ci.org/rust-interview/rust-leetcode-solutions.svg?branch=master)](https://travis-ci.org/rust-interview/rust-leetcode-solutions)
 [![Coverage Status](https://coveralls.io/repos/github/rust-interview/rust-leetcode-solutions/badge.svg?branch=master)](https://coveralls.io/github/rust-interview/rust-leetcode-solutions)
 
+## Acknowledgements
+
++ https://github.com/kamyu104/LeetCode-Solutions
++ https://github.com/begeekmyfriend/leetcode
+
+
 ## [kamyu104's](https://github.com/kamyu104/LeetCode-Solutions)
 ```
 cd kamyu104
@@ -1160,9 +1166,3 @@ cargo test
 1117| [Building H2O](https://leetcode.com/problems/building-h2o/) | [C++](./C++/building-h2o.cpp) [Python](./Python/building-h2o.py) | _O(n)_ | _O(1)_| Hard |||
  -->
 
-
-
-## Acknowledgements
-
-+ https://github.com/kamyu104/LeetCode-Solutions
-+ https://github.com/begeekmyfriend/leetcode
diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index ef557d9..bf87cf3 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -2,12 +2,12 @@
 // Space: O(n)
 // Counting Sort + Pruning + Bit Manipulation
 // https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/maximum-product-of-word-lengths.cpp#L1-L40
-pub struct Solution1 {}
-impl Solution1 {
-    pub fn max_product(words: Vec<String>) -> i32 {
-        0
-    }
-}
+// pub struct Solution1 {}
+// impl Solution1 {
+//     pub fn max_product(words: Vec<String>) -> i32 {
+//         0
+//     }
+// }
 
 // Time:  O(nlogn) ~ O(n^2)
 // Space: O(n)
@@ -45,23 +45,23 @@ impl Solution2 {
 // # Time:  O(n) ~ O(n^2)
 // # Space: O(n)
 // https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-product-of-word-lengths.py#L1-L36
-pub struct Solution3 {}
-impl Solution3 {
-    pub fn max_product(words: Vec<String>) -> i32 {
-        0
-    }
-}
+// pub struct Solution3 {}
+// impl Solution3 {
+//     pub fn max_product(words: Vec<String>) -> i32 {
+//         0
+//     }
+// }
 
 // # Time:  O(nlogn) ~ O(n^2)
 // # Space: O(n)
 // # Sorting + Pruning + Bit Manipulation
 // https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-product-of-word-lengths.py#L38-L62
-pub struct Solution4 {}
-impl Solution4 {
-    pub fn max_product(words: Vec<String>) -> i32 {
-        0
-    }
-}
+// pub struct Solution4 {}
+// impl Solution4 {
+//     pub fn max_product(words: Vec<String>) -> i32 {
+//         0
+//     }
+// }
 
 #[cfg(test)]
 mod tests {

From 96ed4a446a3d8274b74f68dec402dc1772dd55de Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 24 Jul 2019 10:12:55 +0800
Subject: [PATCH 40/82] init for power_of_four

---
 README.md                                       | 2 +-
 kamyu104/src/main.rs                            | 1 +
 kamyu104/src/maximum_product_of_word_lengths.rs | 3 +--
 kamyu104/src/power_of_four.rs                   | 1 +
 4 files changed, 4 insertions(+), 3 deletions(-)
 create mode 100644 kamyu104/src/power_of_four.rs

diff --git a/README.md b/README.md
index a7a34d6..5dfeb29 100644
--- a/README.md
+++ b/README.md
@@ -64,10 +64,10 @@ cargo test
 0260 | [Single Number III](https://leetcode.com/problems/single-number-iii/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/single-number-iii.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/single-number-iii.py) <br>------</br> [Rust](./kamyu104/src/single_number_iii.rs) | _O(n)_ | _O(1)_          | Medium         ||
 0268| [Missing Number](https://leetcode.com/problems/missing-number/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/missing-number.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/missing-number.py) <br>------</br> [Rust](./kamyu104/src/missing_number.rs) | _O(n)_ |  _O(1)_ | Medium         | LintCode ||
 0318| [Maximum Product of Word Lengths](https://leetcode.com/problems/maximum-product-of-word-lengths/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/maximum-product-of-word-lengths.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-product-of-word-lengths.py) <br>------</br> [Rust](./kamyu104/src/maximum_product_of_word_lengths.rs) | _O(n)_ ~ _O(n^2)_ |  _O(n)_ | Medium         || Bit Manipulation, Counting Sort, Pruning|
+0342 | [Power of Four](https://leetcode.com/problems/power-of-four/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/power-of-four.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/power-of-four.py) <br>------</br> [Rust](./kamyu104/src/power_of_four.rs) | _O(1)_ | _O(1)_ | Easy | |
 
 <!-- 
 
-0342 | [Power of Four](https://leetcode.com/problems/power-of-four/) | [C++](./C++/power-of-four.cpp) [Python](./Python/power-of-four.py) | _O(1)_ | _O(1)_ | Easy | |
 0371 | [Sum of Two Integers](https://leetcode.com/problems/sum-of-two-integers/) | [C++](./C++/sum-of-two-integers.cpp) [Python](./Python/sum-of-two-integers.py) | _O(1)_ | _O(1)_ | Easy | LintCode |
 0389 | [Find the Difference](https://leetcode.com/problems/find-the-difference/) | [C++](./C++/find-the-difference.cpp) [Python](./Python/find-the-difference.py) | _O(n)_ | _O(1)_ | Easy | |
 0393 | [UTF-8 Validation](https://leetcode.com/problems/utf-8-validation/) | [C++](./C++/utf-8-validation.cpp) [Python](./Python/utf-8-validation.py) | _O(n)_ | _O(1)_ | Medium | |
diff --git a/kamyu104/src/main.rs b/kamyu104/src/main.rs
index 5c1a2ae..4f40133 100644
--- a/kamyu104/src/main.rs
+++ b/kamyu104/src/main.rs
@@ -2,6 +2,7 @@ mod bitwise_and_of_numbers_range;
 mod maximum_product_of_word_lengths;
 mod missing_number;
 mod number_of_1_bits;
+mod power_of_four;
 mod power_of_two;
 mod reverse_bits;
 mod single_number;
diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index bf87cf3..6cf2e7c 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -41,7 +41,6 @@ impl Solution2 {
     }
 }
 
-
 // # Time:  O(n) ~ O(n^2)
 // # Space: O(n)
 // https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-product-of-word-lengths.py#L1-L36
@@ -97,4 +96,4 @@ mod tests {
             0
         );
     }
-}
\ No newline at end of file
+}
diff --git a/kamyu104/src/power_of_four.rs b/kamyu104/src/power_of_four.rs
new file mode 100644
index 0000000..8b13789
--- /dev/null
+++ b/kamyu104/src/power_of_four.rs
@@ -0,0 +1 @@
+

From 4febd4d61c75de06254a9323c21b15bde5978aae Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 24 Jul 2019 10:16:27 +0800
Subject: [PATCH 41/82] update is_power_of_four

---
 kamyu104/src/power_of_four.rs | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/kamyu104/src/power_of_four.rs b/kamyu104/src/power_of_four.rs
index 8b13789..48668cc 100644
--- a/kamyu104/src/power_of_four.rs
+++ b/kamyu104/src/power_of_four.rs
@@ -1 +1,18 @@
+pub struct Solution {}
+impl Solution {
+    pub fn is_power_of_four(num: i32) -> bool {
+        false
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_is_power_of_four() {
+        assert_eq!(Solution::is_power_of_four(16), true);
+        assert_eq!(Solution::is_power_of_four(5), false);
+    }
+}
 

From f499b80f83b5edf6d91b174e36ff9484c0700b2a Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 24 Jul 2019 11:14:08 +0800
Subject: [PATCH 42/82] add sol1

---
 kamyu104/src/power_of_four.rs | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/kamyu104/src/power_of_four.rs b/kamyu104/src/power_of_four.rs
index 48668cc..22a56a8 100644
--- a/kamyu104/src/power_of_four.rs
+++ b/kamyu104/src/power_of_four.rs
@@ -1,7 +1,10 @@
-pub struct Solution {}
-impl Solution {
+// Time:  O(1)
+// Space: O(1)
+pub struct Solution1 {}
+impl Solution1 {
     pub fn is_power_of_four(num: i32) -> bool {
-        false
+        num > 0 && (num & (num - 1)) == 0 &&
+               ((num & 0b01010101010101010101010101010101) == num)
     }
 }
 
@@ -11,8 +14,8 @@ mod tests {
 
     #[test]
     fn test_is_power_of_four() {
-        assert_eq!(Solution::is_power_of_four(16), true);
-        assert_eq!(Solution::is_power_of_four(5), false);
+        assert_eq!(Solution1::is_power_of_four(16), true);
+        assert_eq!(Solution1::is_power_of_four(5), false);
     }
 }
 

From 1b03a30e248f18ed39b02c985ca9beb8233b48e5 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 24 Jul 2019 11:17:11 +0800
Subject: [PATCH 43/82] add sol2

---
 kamyu104/src/power_of_four.rs | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/kamyu104/src/power_of_four.rs b/kamyu104/src/power_of_four.rs
index 22a56a8..2bb272e 100644
--- a/kamyu104/src/power_of_four.rs
+++ b/kamyu104/src/power_of_four.rs
@@ -3,8 +3,20 @@
 pub struct Solution1 {}
 impl Solution1 {
     pub fn is_power_of_four(num: i32) -> bool {
-        num > 0 && (num & (num - 1)) == 0 &&
-               ((num & 0b01010101010101010101010101010101) == num)
+        num > 0 && (num & (num - 1)) == 0 && ((num & 0b01010101010101010101010101010101) == num)
+    }
+}
+
+// Time:  O(1)
+// Space: O(1)
+pub struct Solution2 {}
+impl Solution2 {
+    pub fn is_power_of_four(num: i32) -> bool {
+        let mut n = num;
+        while (n != 0) && (n & 0b11) == 0 {
+            n >>= 2;
+        }
+        (n == 1)
     }
 }
 
@@ -16,6 +28,8 @@ mod tests {
     fn test_is_power_of_four() {
         assert_eq!(Solution1::is_power_of_four(16), true);
         assert_eq!(Solution1::is_power_of_four(5), false);
+
+        assert_eq!(Solution2::is_power_of_four(16), true);
+        assert_eq!(Solution2::is_power_of_four(5), false);
     }
 }
-

From 2b1c407e7838109ebcee3c8d5dd382d2c02417c5 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 24 Jul 2019 11:17:49 +0800
Subject: [PATCH 44/82] clean

---
 kamyu104/src/power_of_four.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kamyu104/src/power_of_four.rs b/kamyu104/src/power_of_four.rs
index 2bb272e..8ed15e8 100644
--- a/kamyu104/src/power_of_four.rs
+++ b/kamyu104/src/power_of_four.rs
@@ -13,10 +13,10 @@ pub struct Solution2 {}
 impl Solution2 {
     pub fn is_power_of_four(num: i32) -> bool {
         let mut n = num;
-        while (n != 0) && (n & 0b11) == 0 {
+        while n != 0 && (n & 0b11) == 0 {
             n >>= 2;
         }
-        (n == 1)
+        n == 1
     }
 }
 

From 338a5167effb67251a818450448b1a55e3674d77 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 24 Jul 2019 11:20:08 +0800
Subject: [PATCH 45/82] mark sol

---
 kamyu104/src/power_of_four.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/kamyu104/src/power_of_four.rs b/kamyu104/src/power_of_four.rs
index 8ed15e8..d2a3e7f 100644
--- a/kamyu104/src/power_of_four.rs
+++ b/kamyu104/src/power_of_four.rs
@@ -20,6 +20,13 @@ impl Solution2 {
     }
 }
 
+// https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/power-of-four.py#L27-L34
+// pub struct Solution3 {}
+// impl Solution3 {
+//     pub fn is_power_of_four(num: i32) -> bool {
+//     }
+// }
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -31,5 +38,8 @@ mod tests {
 
         assert_eq!(Solution2::is_power_of_four(16), true);
         assert_eq!(Solution2::is_power_of_four(5), false);
+
+        // assert_eq!(Solution3::is_power_of_four(16), true);
+        // assert_eq!(Solution3::is_power_of_four(5), false);
     }
 }

From 81589bdc4603867d2cd9a91f554ce9aab7830649 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 24 Jul 2019 13:39:40 +0800
Subject: [PATCH 46/82] init get_sum

---
 kamyu104/src/main.rs                |  1 +
 kamyu104/src/sum_of_two_integers.rs | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+)
 create mode 100644 kamyu104/src/sum_of_two_integers.rs

diff --git a/kamyu104/src/main.rs b/kamyu104/src/main.rs
index 4f40133..8c1b6e4 100644
--- a/kamyu104/src/main.rs
+++ b/kamyu104/src/main.rs
@@ -8,4 +8,5 @@ mod reverse_bits;
 mod single_number;
 mod single_number_ii;
 mod single_number_iii;
+mod sum_of_two_integers;
 mod template;
diff --git a/kamyu104/src/sum_of_two_integers.rs b/kamyu104/src/sum_of_two_integers.rs
new file mode 100644
index 0000000..7f3435c
--- /dev/null
+++ b/kamyu104/src/sum_of_two_integers.rs
@@ -0,0 +1,18 @@
+pub struct Solution {}
+impl Solution {
+    pub fn get_sum(a: i32, b: i32) -> i32 {
+        0
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    // Note this useful idiom: importing names from outer (for mod tests) scope.
+    use super::*;
+
+    #[test]
+    fn test_get_sum() {
+        assert_eq!(Solution::get_sum(1, 2), 3);
+        assert_eq!(Solution::get_sum(-2, 3), 1);
+    }
+}

From 2364c69c316105a618752c9e9501badd4a80676a Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 24 Jul 2019 13:41:29 +0800
Subject: [PATCH 47/82] fix readme

---
 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 5dfeb29..93c1815 100644
--- a/README.md
+++ b/README.md
@@ -65,10 +65,10 @@ cargo test
 0268| [Missing Number](https://leetcode.com/problems/missing-number/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/missing-number.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/missing-number.py) <br>------</br> [Rust](./kamyu104/src/missing_number.rs) | _O(n)_ |  _O(1)_ | Medium         | LintCode ||
 0318| [Maximum Product of Word Lengths](https://leetcode.com/problems/maximum-product-of-word-lengths/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/maximum-product-of-word-lengths.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-product-of-word-lengths.py) <br>------</br> [Rust](./kamyu104/src/maximum_product_of_word_lengths.rs) | _O(n)_ ~ _O(n^2)_ |  _O(n)_ | Medium         || Bit Manipulation, Counting Sort, Pruning|
 0342 | [Power of Four](https://leetcode.com/problems/power-of-four/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/power-of-four.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/power-of-four.py) <br>------</br> [Rust](./kamyu104/src/power_of_four.rs) | _O(1)_ | _O(1)_ | Easy | |
+0371 | [Sum of Two Integers](https://leetcode.com/problems/sum-of-two-integers/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/sum-of-two-integers.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/sum-of-two-integers.py) <br>------</br> [Rust](./kamyu104/src/sum_of_two_integers.rs) | _O(1)_ | _O(1)_ | Easy | LintCode |
 
 <!-- 
 
-0371 | [Sum of Two Integers](https://leetcode.com/problems/sum-of-two-integers/) | [C++](./C++/sum-of-two-integers.cpp) [Python](./Python/sum-of-two-integers.py) | _O(1)_ | _O(1)_ | Easy | LintCode |
 0389 | [Find the Difference](https://leetcode.com/problems/find-the-difference/) | [C++](./C++/find-the-difference.cpp) [Python](./Python/find-the-difference.py) | _O(n)_ | _O(1)_ | Easy | |
 0393 | [UTF-8 Validation](https://leetcode.com/problems/utf-8-validation/) | [C++](./C++/utf-8-validation.cpp) [Python](./Python/utf-8-validation.py) | _O(n)_ | _O(1)_ | Medium | |
 0401 | [Binary Watch](https://leetcode.com/problems/binary-watch/) | [C++](./C++/binary-watch.cpp) [Python](./Python/binary-watch.py) | _O(1)_ | _O(1)_ | Easy | |

From 9fe0f8e61c2a7164b1d7dd8d18f14ea47e683d2e Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 24 Jul 2019 13:45:33 +0800
Subject: [PATCH 48/82] add get_sum sol1

---
 kamyu104/src/sum_of_two_integers.rs | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/kamyu104/src/sum_of_two_integers.rs b/kamyu104/src/sum_of_two_integers.rs
index 7f3435c..c45d9ed 100644
--- a/kamyu104/src/sum_of_two_integers.rs
+++ b/kamyu104/src/sum_of_two_integers.rs
@@ -1,7 +1,16 @@
+// Time:  O(1)
+// Space: O(1)
 pub struct Solution {}
 impl Solution {
     pub fn get_sum(a: i32, b: i32) -> i32 {
-        0
+        let mut ma = a.clone();
+        let mut mb = b.clone();
+        while mb != 0 {
+            let carry = ma & mb;
+            ma ^= mb;
+            mb = carry << 1;
+        }
+        ma
     }
 }
 

From 61d04ac652d36f567b585b83e0b30b0c4b6443e4 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 24 Jul 2019 18:36:18 +0800
Subject: [PATCH 49/82] wip

---
 kamyu104/src/sum_of_two_integers.rs | 51 ++++++++++++++++++++++++++---
 1 file changed, 47 insertions(+), 4 deletions(-)

diff --git a/kamyu104/src/sum_of_two_integers.rs b/kamyu104/src/sum_of_two_integers.rs
index c45d9ed..76c0219 100644
--- a/kamyu104/src/sum_of_two_integers.rs
+++ b/kamyu104/src/sum_of_two_integers.rs
@@ -1,7 +1,8 @@
 // Time:  O(1)
 // Space: O(1)
-pub struct Solution {}
-impl Solution {
+
+pub struct Solution1 {}
+impl Solution1 {
     pub fn get_sum(a: i32, b: i32) -> i32 {
         let mut ma = a.clone();
         let mut mb = b.clone();
@@ -14,6 +15,45 @@ impl Solution {
     }
 }
 
+pub struct Solution2 {}
+impl Solution2 {
+    pub fn get_sum(a: i32, b: i32) -> i32 {
+        let bit_length = 32;
+        let neg_bit = (1 << bit_length) >> 1;
+        let mask = !(!0 << bit_length);
+
+        let mut ma = a & mask;
+        if a & neg_bit != 0 {
+            ma = a | !mask;
+        }
+
+        let mut mb = b & mask;
+        if b & neg_bit != 0 {
+            mb = b | !mask;
+        }
+
+        while mb != 0 {
+            let carry = ma & mb;
+            ma ^= mb;
+            if ma & neg_bit != 0 {
+                ma = ma | !mask;
+            } else {
+                ma = ma & mask;
+            }
+            mb = carry << 1;
+            if mb & neg_bit != 0 {
+                mb = mb | !mask;
+            } else {
+                mb = mb & mask;
+            }
+        }
+        a
+    }
+}
+
+pub struct Solution3 {}
+impl Solution3 {}
+
 #[cfg(test)]
 mod tests {
     // Note this useful idiom: importing names from outer (for mod tests) scope.
@@ -21,7 +61,10 @@ mod tests {
 
     #[test]
     fn test_get_sum() {
-        assert_eq!(Solution::get_sum(1, 2), 3);
-        assert_eq!(Solution::get_sum(-2, 3), 1);
+        assert_eq!(Solution1::get_sum(1, 2), 3);
+        assert_eq!(Solution1::get_sum(-2, 3), 1);
+
+        assert_eq!(Solution2::get_sum(1, 2), 3);
+        assert_eq!(Solution2::get_sum(-2, 3), 1);
     }
 }

From 4bc66849d5497419a109cc7c9d1c788bcf0cc644 Mon Sep 17 00:00:00 2001
From: ChrisLinn <nanyishanshaoxiu@gmail.com>
Date: Wed, 24 Jul 2019 21:12:15 +0800
Subject: [PATCH 50/82] refactor

---
 .../src/maximum_product_of_word_lengths.rs    | 17 ++--
 kamyu104/src/power_of_four.rs                 |  9 +-
 kamyu104/src/sum_of_two_integers.rs           | 88 +++++++++----------
 3 files changed, 55 insertions(+), 59 deletions(-)

diff --git a/kamyu104/src/maximum_product_of_word_lengths.rs b/kamyu104/src/maximum_product_of_word_lengths.rs
index 6cf2e7c..c217e50 100644
--- a/kamyu104/src/maximum_product_of_word_lengths.rs
+++ b/kamyu104/src/maximum_product_of_word_lengths.rs
@@ -14,24 +14,21 @@
 // Sorting + Pruning + Bit Manipulation
 pub struct Solution2 {}
 impl Solution2 {
-    pub fn max_product(words: Vec<String>) -> i32 {
-        let mut sorted_words = words.clone();
-        sorted_words.sort_by(|a, b| b.len().cmp(&a.len()));
+    pub fn max_product(mut words: Vec<String>) -> i32 {
+        words.sort_by(|a, b| b.len().cmp(&a.len()));
         let mut bits: Vec<i32> = vec![0; words.len()];
-        for i in 0..sorted_words.len() {
-            for c in sorted_words[i].chars() {
+        for i in 0..words.len() {
+            for c in words[i].chars() {
                 bits[i] |= 1 << (c as u32 - 'a' as u32);
             }
         }
         let mut max_product: i32 = 0;
         let mut i: usize = 0;
-        while i + 1 < sorted_words.len() && sorted_words[i].len().pow(2) as i32 > max_product {
+        while i + 1 < words.len() && words[i].len().pow(2) as i32 > max_product {
             let mut j: usize = i + 1;
-            while j < sorted_words.len()
-                && (sorted_words[i].len() * sorted_words[j].len()) as i32 > max_product
-            {
+            while j < words.len() && (words[i].len() * words[j].len()) as i32 > max_product {
                 if bits[i] & bits[j] == 0 {
-                    max_product = (sorted_words[i].len() * sorted_words[j].len()) as i32;
+                    max_product = (words[i].len() * words[j].len()) as i32;
                 }
                 j += 1;
             }
diff --git a/kamyu104/src/power_of_four.rs b/kamyu104/src/power_of_four.rs
index d2a3e7f..cf6d016 100644
--- a/kamyu104/src/power_of_four.rs
+++ b/kamyu104/src/power_of_four.rs
@@ -11,12 +11,11 @@ impl Solution1 {
 // Space: O(1)
 pub struct Solution2 {}
 impl Solution2 {
-    pub fn is_power_of_four(num: i32) -> bool {
-        let mut n = num;
-        while n != 0 && (n & 0b11) == 0 {
-            n >>= 2;
+    pub fn is_power_of_four(mut num: i32) -> bool {
+        while num != 0 && (num & 0b11) == 0 {
+            num >>= 2;
         }
-        n == 1
+        num == 1
     }
 }
 
diff --git a/kamyu104/src/sum_of_two_integers.rs b/kamyu104/src/sum_of_two_integers.rs
index 76c0219..8c4f9bd 100644
--- a/kamyu104/src/sum_of_two_integers.rs
+++ b/kamyu104/src/sum_of_two_integers.rs
@@ -3,56 +3,56 @@
 
 pub struct Solution1 {}
 impl Solution1 {
-    pub fn get_sum(a: i32, b: i32) -> i32 {
-        let mut ma = a.clone();
-        let mut mb = b.clone();
-        while mb != 0 {
-            let carry = ma & mb;
-            ma ^= mb;
-            mb = carry << 1;
+    pub fn get_sum(mut a: i32, mut b: i32) -> i32 {
+        // let mut ma = a.clone();
+        // let mut mb = b.clone();
+        while b != 0 {
+            let carry = a & b;
+            a ^= b;
+            b = carry << 1;
         }
-        ma
+        a
     }
 }
 
-pub struct Solution2 {}
-impl Solution2 {
-    pub fn get_sum(a: i32, b: i32) -> i32 {
-        let bit_length = 32;
-        let neg_bit = (1 << bit_length) >> 1;
-        let mask = !(!0 << bit_length);
+// pub struct Solution2 {}
+// impl Solution2 {
+//     pub fn get_sum(a: i32, b: i32) -> i32 {
+//         let bit_length = 32;
+//         let neg_bit = (1 << bit_length) >> 1;
+//         let mask = !(!0 << bit_length);
 
-        let mut ma = a & mask;
-        if a & neg_bit != 0 {
-            ma = a | !mask;
-        }
+//         let mut ma = a & mask;
+//         if a & neg_bit != 0 {
+//             ma = a | !mask;
+//         }
 
-        let mut mb = b & mask;
-        if b & neg_bit != 0 {
-            mb = b | !mask;
-        }
+//         let mut mb = b & mask;
+//         if b & neg_bit != 0 {
+//             mb = b | !mask;
+//         }
 
-        while mb != 0 {
-            let carry = ma & mb;
-            ma ^= mb;
-            if ma & neg_bit != 0 {
-                ma = ma | !mask;
-            } else {
-                ma = ma & mask;
-            }
-            mb = carry << 1;
-            if mb & neg_bit != 0 {
-                mb = mb | !mask;
-            } else {
-                mb = mb & mask;
-            }
-        }
-        a
-    }
-}
+//         while mb != 0 {
+//             let carry = ma & mb;
+//             ma ^= mb;
+//             if ma & neg_bit != 0 {
+//                 ma = ma | !mask;
+//             } else {
+//                 ma = ma & mask;
+//             }
+//             mb = carry << 1;
+//             if mb & neg_bit != 0 {
+//                 mb = mb | !mask;
+//             } else {
+//                 mb = mb & mask;
+//             }
+//         }
+//         a
+//     }
+// }
 
-pub struct Solution3 {}
-impl Solution3 {}
+// pub struct Solution3 {}
+// impl Solution3 {}
 
 #[cfg(test)]
 mod tests {
@@ -64,7 +64,7 @@ mod tests {
         assert_eq!(Solution1::get_sum(1, 2), 3);
         assert_eq!(Solution1::get_sum(-2, 3), 1);
 
-        assert_eq!(Solution2::get_sum(1, 2), 3);
-        assert_eq!(Solution2::get_sum(-2, 3), 1);
+        // assert_eq!(Solution2::get_sum(1, 2), 3);
+        // assert_eq!(Solution2::get_sum(-2, 3), 1);
     }
 }

From c3c31e3193da30db6f3b44d19f58b1f047314988 Mon Sep 17 00:00:00 2001
From: ChrisLinn <nanyishanshaoxiu@gmail.com>
Date: Wed, 24 Jul 2019 21:17:08 +0800
Subject: [PATCH 51/82] refactor

---
 kamyu104/src/sum_of_two_integers.rs | 2 --
 1 file changed, 2 deletions(-)

diff --git a/kamyu104/src/sum_of_two_integers.rs b/kamyu104/src/sum_of_two_integers.rs
index 8c4f9bd..8645aa2 100644
--- a/kamyu104/src/sum_of_two_integers.rs
+++ b/kamyu104/src/sum_of_two_integers.rs
@@ -4,8 +4,6 @@
 pub struct Solution1 {}
 impl Solution1 {
     pub fn get_sum(mut a: i32, mut b: i32) -> i32 {
-        // let mut ma = a.clone();
-        // let mut mb = b.clone();
         while b != 0 {
             let carry = a & b;
             a ^= b;

From cdcb3c7250ef26d7b25796ea88f0fc7653e4c6f6 Mon Sep 17 00:00:00 2001
From: ChrisLinn <nanyishanshaoxiu@gmail.com>
Date: Wed, 24 Jul 2019 21:19:28 +0800
Subject: [PATCH 52/82] add

---
 kamyu104/src/sum_of_two_integers.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kamyu104/src/sum_of_two_integers.rs b/kamyu104/src/sum_of_two_integers.rs
index 8645aa2..0f75505 100644
--- a/kamyu104/src/sum_of_two_integers.rs
+++ b/kamyu104/src/sum_of_two_integers.rs
@@ -64,5 +64,8 @@ mod tests {
 
         // assert_eq!(Solution2::get_sum(1, 2), 3);
         // assert_eq!(Solution2::get_sum(-2, 3), 1);
+
+        // assert_eq!(Solution3::get_sum(1, 2), 3);
+        // assert_eq!(Solution3::get_sum(-2, 3), 1);
     }
 }

From f16dfb1a6921da722bdf7720be93c6a9d1c8ddd9 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Thu, 25 Jul 2019 08:08:53 +0800
Subject: [PATCH 53/82] add find_the_difference

---
 kamyu104/src/find_the_difference.rs | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 kamyu104/src/find_the_difference.rs

diff --git a/kamyu104/src/find_the_difference.rs b/kamyu104/src/find_the_difference.rs
new file mode 100644
index 0000000..e69de29

From 2eb45aa0590bc20a68215a556f5aab76890df1e1 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Thu, 25 Jul 2019 08:14:19 +0800
Subject: [PATCH 54/82] add

---
 README.md            | 2 +-
 kamyu104/src/main.rs | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 93c1815..3d99927 100644
--- a/README.md
+++ b/README.md
@@ -66,10 +66,10 @@ cargo test
 0318| [Maximum Product of Word Lengths](https://leetcode.com/problems/maximum-product-of-word-lengths/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/maximum-product-of-word-lengths.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-product-of-word-lengths.py) <br>------</br> [Rust](./kamyu104/src/maximum_product_of_word_lengths.rs) | _O(n)_ ~ _O(n^2)_ |  _O(n)_ | Medium         || Bit Manipulation, Counting Sort, Pruning|
 0342 | [Power of Four](https://leetcode.com/problems/power-of-four/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/power-of-four.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/power-of-four.py) <br>------</br> [Rust](./kamyu104/src/power_of_four.rs) | _O(1)_ | _O(1)_ | Easy | |
 0371 | [Sum of Two Integers](https://leetcode.com/problems/sum-of-two-integers/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/sum-of-two-integers.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/sum-of-two-integers.py) <br>------</br> [Rust](./kamyu104/src/sum_of_two_integers.rs) | _O(1)_ | _O(1)_ | Easy | LintCode |
+0389 | [Find the Difference](https://leetcode.com/problems/find-the-difference/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/find-the-difference.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/find-the-difference.py) <br>------</br> [Rust](./kamyu104/src/find_the_difference.rs) | _O(n)_ | _O(1)_ | Easy | |
 
 <!-- 
 
-0389 | [Find the Difference](https://leetcode.com/problems/find-the-difference/) | [C++](./C++/find-the-difference.cpp) [Python](./Python/find-the-difference.py) | _O(n)_ | _O(1)_ | Easy | |
 0393 | [UTF-8 Validation](https://leetcode.com/problems/utf-8-validation/) | [C++](./C++/utf-8-validation.cpp) [Python](./Python/utf-8-validation.py) | _O(n)_ | _O(1)_ | Medium | |
 0401 | [Binary Watch](https://leetcode.com/problems/binary-watch/) | [C++](./C++/binary-watch.cpp) [Python](./Python/binary-watch.py) | _O(1)_ | _O(1)_ | Easy | |
 0411 | [Minimum Unique Word Abbreviation](https://leetcode.com/problems/minimum-unique-word-abbreviation/) | [C++](./C++/minimum-unique-word-abbreviation.cpp) [Python](./Python/minimum-unique-word-abbreviation.py) | _O(2^n)_ | _O(n)_ | Hard | 🔒 |
diff --git a/kamyu104/src/main.rs b/kamyu104/src/main.rs
index 8c1b6e4..70783a1 100644
--- a/kamyu104/src/main.rs
+++ b/kamyu104/src/main.rs
@@ -9,4 +9,5 @@ mod single_number;
 mod single_number_ii;
 mod single_number_iii;
 mod sum_of_two_integers;
+mod find_the_difference;
 mod template;

From 0e87d6ee4483353b5f50db18ab7f86fdb7dfba41 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Thu, 25 Jul 2019 08:18:14 +0800
Subject: [PATCH 55/82] draft

---
 kamyu104/src/find_the_difference.rs | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/kamyu104/src/find_the_difference.rs b/kamyu104/src/find_the_difference.rs
index e69de29..bb57aa9 100644
--- a/kamyu104/src/find_the_difference.rs
+++ b/kamyu104/src/find_the_difference.rs
@@ -0,0 +1,17 @@
+pub struct Solution {}
+impl Solution {
+    pub fn find_the_difference(s: String, t: String) -> char {
+        'e'
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    // Note this useful idiom: importing names from outer (for mod tests) scope.
+    use super::*;
+
+    #[test]
+    fn test_find_the_difference() {
+        assert_eq!(Solution::find_the_difference("abcd".to_string(), "abcde".to_string()), 'e');
+    }
+}

From cef2b1e7301120e400e6d4b130e519abfeef030c Mon Sep 17 00:00:00 2001
From: ChrisLinn <nanyishanshaoxiu@gmail.com>
Date: Fri, 26 Jul 2019 19:20:09 +0800
Subject: [PATCH 56/82] init utf_8_validation

---
 README.md                           |  2 +-
 kamyu104/src/find_the_difference.rs | 14 +++++++-------
 kamyu104/src/main.rs                |  1 +
 kamyu104/src/utf_8_validation.rs    |  0
 4 files changed, 9 insertions(+), 8 deletions(-)
 create mode 100644 kamyu104/src/utf_8_validation.rs

diff --git a/README.md b/README.md
index 3d99927..1857e98 100644
--- a/README.md
+++ b/README.md
@@ -67,10 +67,10 @@ cargo test
 0342 | [Power of Four](https://leetcode.com/problems/power-of-four/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/power-of-four.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/power-of-four.py) <br>------</br> [Rust](./kamyu104/src/power_of_four.rs) | _O(1)_ | _O(1)_ | Easy | |
 0371 | [Sum of Two Integers](https://leetcode.com/problems/sum-of-two-integers/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/sum-of-two-integers.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/sum-of-two-integers.py) <br>------</br> [Rust](./kamyu104/src/sum_of_two_integers.rs) | _O(1)_ | _O(1)_ | Easy | LintCode |
 0389 | [Find the Difference](https://leetcode.com/problems/find-the-difference/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/find-the-difference.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/find-the-difference.py) <br>------</br> [Rust](./kamyu104/src/find_the_difference.rs) | _O(n)_ | _O(1)_ | Easy | |
+0393 | [UTF-8 Validation](https://leetcode.com/problems/utf-8-validation/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/utf-8-validation.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/utf-8-validation.py) <br>------</br> [Rust](./kamyu104/src/utf_8_validation.rs) | _O(n)_ | _O(1)_ | Medium | |
 
 <!-- 
 
-0393 | [UTF-8 Validation](https://leetcode.com/problems/utf-8-validation/) | [C++](./C++/utf-8-validation.cpp) [Python](./Python/utf-8-validation.py) | _O(n)_ | _O(1)_ | Medium | |
 0401 | [Binary Watch](https://leetcode.com/problems/binary-watch/) | [C++](./C++/binary-watch.cpp) [Python](./Python/binary-watch.py) | _O(1)_ | _O(1)_ | Easy | |
 0411 | [Minimum Unique Word Abbreviation](https://leetcode.com/problems/minimum-unique-word-abbreviation/) | [C++](./C++/minimum-unique-word-abbreviation.cpp) [Python](./Python/minimum-unique-word-abbreviation.py) | _O(2^n)_ | _O(n)_ | Hard | 🔒 |
 0421 | [Maximum XOR of Two Numbers in an Array](https://leetcode.com/problems/maximum-xor-of-two-numbers-in-an-array/) | [C++](./C++/maximum-xor-of-two-numbers-in-an-array.cpp) [Python](./Python/maximum-xor-of-two-numbers-in-an-array.py) | _O(n)_ | _O(n)_ | Medium ||
diff --git a/kamyu104/src/find_the_difference.rs b/kamyu104/src/find_the_difference.rs
index bb57aa9..ea7bf3c 100644
--- a/kamyu104/src/find_the_difference.rs
+++ b/kamyu104/src/find_the_difference.rs
@@ -1,9 +1,9 @@
-pub struct Solution {}
-impl Solution {
-    pub fn find_the_difference(s: String, t: String) -> char {
-        'e'
-    }
-}
+// pub struct Solution {}
+// impl Solution {
+//     pub fn find_the_difference(s: String, t: String) -> char {
+//         'e'
+//     }
+// }
 
 #[cfg(test)]
 mod tests {
@@ -12,6 +12,6 @@ mod tests {
 
     #[test]
     fn test_find_the_difference() {
-        assert_eq!(Solution::find_the_difference("abcd".to_string(), "abcde".to_string()), 'e');
+        // assert_eq!(Solution::find_the_difference("abcd".to_string(), "abcde".to_string()), 'e');
     }
 }
diff --git a/kamyu104/src/main.rs b/kamyu104/src/main.rs
index 70783a1..7b90290 100644
--- a/kamyu104/src/main.rs
+++ b/kamyu104/src/main.rs
@@ -10,4 +10,5 @@ mod single_number_ii;
 mod single_number_iii;
 mod sum_of_two_integers;
 mod find_the_difference;
+mod utf_8_validation;
 mod template;
diff --git a/kamyu104/src/utf_8_validation.rs b/kamyu104/src/utf_8_validation.rs
new file mode 100644
index 0000000..e69de29

From 946feabc93db32daf07d30ecdcd47effede9714e Mon Sep 17 00:00:00 2001
From: ChrisLinn <nanyishanshaoxiu@gmail.com>
Date: Fri, 26 Jul 2019 19:26:23 +0800
Subject: [PATCH 57/82] add valid_utf8

---
 README.md                        |  2 +-
 kamyu104/src/utf_8_validation.rs | 17 +++++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 1857e98..3c452f1 100644
--- a/README.md
+++ b/README.md
@@ -66,7 +66,7 @@ cargo test
 0318| [Maximum Product of Word Lengths](https://leetcode.com/problems/maximum-product-of-word-lengths/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/maximum-product-of-word-lengths.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-product-of-word-lengths.py) <br>------</br> [Rust](./kamyu104/src/maximum_product_of_word_lengths.rs) | _O(n)_ ~ _O(n^2)_ |  _O(n)_ | Medium         || Bit Manipulation, Counting Sort, Pruning|
 0342 | [Power of Four](https://leetcode.com/problems/power-of-four/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/power-of-four.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/power-of-four.py) <br>------</br> [Rust](./kamyu104/src/power_of_four.rs) | _O(1)_ | _O(1)_ | Easy | |
 0371 | [Sum of Two Integers](https://leetcode.com/problems/sum-of-two-integers/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/sum-of-two-integers.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/sum-of-two-integers.py) <br>------</br> [Rust](./kamyu104/src/sum_of_two_integers.rs) | _O(1)_ | _O(1)_ | Easy | LintCode |
-0389 | [Find the Difference](https://leetcode.com/problems/find-the-difference/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/find-the-difference.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/find-the-difference.py) <br>------</br> [Rust](./kamyu104/src/find_the_difference.rs) | _O(n)_ | _O(1)_ | Easy | |
+0389 | [~~Find the Difference~~](https://leetcode.com/problems/find-the-difference/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/find-the-difference.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/find-the-difference.py) <br>------</br> [Rust](./kamyu104/src/find_the_difference.rs) | _O(n)_ | _O(1)_ | Easy | |
 0393 | [UTF-8 Validation](https://leetcode.com/problems/utf-8-validation/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/utf-8-validation.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/utf-8-validation.py) <br>------</br> [Rust](./kamyu104/src/utf_8_validation.rs) | _O(n)_ | _O(1)_ | Medium | |
 
 <!-- 
diff --git a/kamyu104/src/utf_8_validation.rs b/kamyu104/src/utf_8_validation.rs
index e69de29..43bd1ff 100644
--- a/kamyu104/src/utf_8_validation.rs
+++ b/kamyu104/src/utf_8_validation.rs
@@ -0,0 +1,17 @@
+pub struct Solution {}
+impl Solution {
+    pub fn valid_utf8(data: Vec<i32>) -> bool {
+        true
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_valid_utf8() {
+        assert_eq!(Solution::valid_utf8(vec![197, 130, 1]), true);
+        assert_eq!(Solution::valid_utf8(vec![235, 140, 4]), false);
+    }
+}

From bd522ea88a1640f77d26d6ef64fffbceb2862cd2 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 31 Jul 2019 10:56:00 +0800
Subject: [PATCH 58/82] add utf_8_validation

---
 kamyu104/src/utf_8_validation.rs | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/kamyu104/src/utf_8_validation.rs b/kamyu104/src/utf_8_validation.rs
index 43bd1ff..73f3acd 100644
--- a/kamyu104/src/utf_8_validation.rs
+++ b/kamyu104/src/utf_8_validation.rs
@@ -1,7 +1,31 @@
+// Time:  O(n)
+// Space: O(1)
 pub struct Solution {}
 impl Solution {
     pub fn valid_utf8(data: Vec<i32>) -> bool {
-        true
+        let mut count: i32 = 0;
+        for c in data {
+            match count {
+                0 => {
+                    if (c >> 5) == 0b110 {
+                        count = 1;
+                    } else if (c >> 4) == 0b1110 {
+                        count = 2;
+                    } else if (c >> 3) == 0b11110 {
+                        count = 3;
+                    } else if c >> 7!=0 {
+                        return false;
+                    }
+                },
+                _ => {
+                    if (c >> 6) != 0b10 {
+                        return false;
+                    }
+                    count-=1;
+                },
+            }
+        }
+        count == 0
     }
 }
 

From 59437e2f35a7b28243e20e97ecdf27c93a0a0b1b Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 31 Jul 2019 10:57:38 +0800
Subject: [PATCH 59/82] cargo fmt

---
 kamyu104/src/main.rs             | 4 ++--
 kamyu104/src/utf_8_validation.rs | 8 ++++----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/kamyu104/src/main.rs b/kamyu104/src/main.rs
index 7b90290..2d7e902 100644
--- a/kamyu104/src/main.rs
+++ b/kamyu104/src/main.rs
@@ -1,4 +1,5 @@
 mod bitwise_and_of_numbers_range;
+mod find_the_difference;
 mod maximum_product_of_word_lengths;
 mod missing_number;
 mod number_of_1_bits;
@@ -9,6 +10,5 @@ mod single_number;
 mod single_number_ii;
 mod single_number_iii;
 mod sum_of_two_integers;
-mod find_the_difference;
-mod utf_8_validation;
 mod template;
+mod utf_8_validation;
diff --git a/kamyu104/src/utf_8_validation.rs b/kamyu104/src/utf_8_validation.rs
index 73f3acd..2831c8b 100644
--- a/kamyu104/src/utf_8_validation.rs
+++ b/kamyu104/src/utf_8_validation.rs
@@ -13,16 +13,16 @@ impl Solution {
                         count = 2;
                     } else if (c >> 3) == 0b11110 {
                         count = 3;
-                    } else if c >> 7!=0 {
+                    } else if c >> 7 != 0 {
                         return false;
                     }
-                },
+                }
                 _ => {
                     if (c >> 6) != 0b10 {
                         return false;
                     }
-                    count-=1;
-                },
+                    count -= 1;
+                }
             }
         }
         count == 0

From 31d6d39a534fe2a66dab6b1efc4283a3f332da9c Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 31 Jul 2019 13:47:32 +0800
Subject: [PATCH 60/82] add sol3

---
 kamyu104/src/find_the_difference.rs | 56 ++++++++++++++++++++++++++---
 1 file changed, 52 insertions(+), 4 deletions(-)

diff --git a/kamyu104/src/find_the_difference.rs b/kamyu104/src/find_the_difference.rs
index ea7bf3c..9215946 100644
--- a/kamyu104/src/find_the_difference.rs
+++ b/kamyu104/src/find_the_difference.rs
@@ -1,5 +1,51 @@
-// pub struct Solution {}
-// impl Solution {
+use std::collections::HashSet;
+
+// Time:  O(n)
+// Space: O(1)
+
+// pub struct Solution1 {}
+// impl Solution1 {
+//     pub fn find_the_difference(s: String, t: String) -> char {
+//         'e'
+//     }
+// }
+
+// pub struct Solution2 {}
+// impl Solution2 {
+//     pub fn find_the_difference(s: String, t: String) -> char {
+//         'e'
+//     }
+// }
+
+// https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/find-the-difference.py#L18
+pub struct Solution3 {}
+impl Solution3 {
+    pub fn find_the_difference(s: String, t: String) -> char {
+        let s_chars: HashSet<char> = s.chars().collect();
+        let mut t_chars: HashSet<char> = t.chars().collect();
+        s_chars.iter().for_each(|c| {
+            t_chars.remove(c);
+        });
+        t_chars.into_iter().collect::<Vec<char>>()[0]
+    }
+}
+
+// pub struct Solution4 {}
+// impl Solution4 {
+//     pub fn find_the_difference(s: String, t: String) -> char {
+//         'e'
+//     }
+// }
+
+// pub struct Solution5 {}
+// impl Solution5 {
+//     pub fn find_the_difference(s: String, t: String) -> char {
+//         'e'
+//     }
+// }
+
+// pub struct Solution6 {}
+// impl Solution6 {
 //     pub fn find_the_difference(s: String, t: String) -> char {
 //         'e'
 //     }
@@ -7,11 +53,13 @@
 
 #[cfg(test)]
 mod tests {
-    // Note this useful idiom: importing names from outer (for mod tests) scope.
     use super::*;
 
     #[test]
     fn test_find_the_difference() {
-        // assert_eq!(Solution::find_the_difference("abcd".to_string(), "abcde".to_string()), 'e');
+        assert_eq!(
+            Solution3::find_the_difference("abcd".to_string(), "abcde".to_string()),
+            'e'
+        );
     }
 }

From 56ebeeabdf3363b4fc89ea6d6bb5402b03ab62b7 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 31 Jul 2019 13:47:50 +0800
Subject: [PATCH 61/82] clean up

---
 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 3c452f1..1857e98 100644
--- a/README.md
+++ b/README.md
@@ -66,7 +66,7 @@ cargo test
 0318| [Maximum Product of Word Lengths](https://leetcode.com/problems/maximum-product-of-word-lengths/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/maximum-product-of-word-lengths.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-product-of-word-lengths.py) <br>------</br> [Rust](./kamyu104/src/maximum_product_of_word_lengths.rs) | _O(n)_ ~ _O(n^2)_ |  _O(n)_ | Medium         || Bit Manipulation, Counting Sort, Pruning|
 0342 | [Power of Four](https://leetcode.com/problems/power-of-four/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/power-of-four.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/power-of-four.py) <br>------</br> [Rust](./kamyu104/src/power_of_four.rs) | _O(1)_ | _O(1)_ | Easy | |
 0371 | [Sum of Two Integers](https://leetcode.com/problems/sum-of-two-integers/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/sum-of-two-integers.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/sum-of-two-integers.py) <br>------</br> [Rust](./kamyu104/src/sum_of_two_integers.rs) | _O(1)_ | _O(1)_ | Easy | LintCode |
-0389 | [~~Find the Difference~~](https://leetcode.com/problems/find-the-difference/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/find-the-difference.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/find-the-difference.py) <br>------</br> [Rust](./kamyu104/src/find_the_difference.rs) | _O(n)_ | _O(1)_ | Easy | |
+0389 | [Find the Difference](https://leetcode.com/problems/find-the-difference/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/find-the-difference.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/find-the-difference.py) <br>------</br> [Rust](./kamyu104/src/find_the_difference.rs) | _O(n)_ | _O(1)_ | Easy | |
 0393 | [UTF-8 Validation](https://leetcode.com/problems/utf-8-validation/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/utf-8-validation.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/utf-8-validation.py) <br>------</br> [Rust](./kamyu104/src/utf_8_validation.rs) | _O(n)_ | _O(1)_ | Medium | |
 
 <!-- 

From a753940a8561af18db72080c41d596a1b756545a Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 31 Jul 2019 14:14:43 +0800
Subject: [PATCH 62/82] fix

---
 kamyu104/src/find_the_difference.rs | 32 ++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/kamyu104/src/find_the_difference.rs b/kamyu104/src/find_the_difference.rs
index 9215946..4dc9cda 100644
--- a/kamyu104/src/find_the_difference.rs
+++ b/kamyu104/src/find_the_difference.rs
@@ -17,16 +17,14 @@ use std::collections::HashSet;
 //     }
 // }
 
-// https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/find-the-difference.py#L18
 pub struct Solution3 {}
 impl Solution3 {
     pub fn find_the_difference(s: String, t: String) -> char {
         let s_chars: HashSet<char> = s.chars().collect();
-        let mut t_chars: HashSet<char> = t.chars().collect();
-        s_chars.iter().for_each(|c| {
-            t_chars.remove(c);
-        });
-        t_chars.into_iter().collect::<Vec<char>>()[0]
+        let t_chars: HashSet<char> = t.chars().collect();
+        // or https://doc.rust-lang.org/std/collections/struct.HashSet.html#method.symmetric_difference
+        let diff: HashSet<&char> = t_chars.difference(&s_chars).collect(); 
+        *(diff.into_iter().collect::<Vec<&char>>()[0])
     }
 }
 
@@ -37,12 +35,18 @@ impl Solution3 {
 //     }
 // }
 
-// pub struct Solution5 {}
-// impl Solution5 {
-//     pub fn find_the_difference(s: String, t: String) -> char {
-//         'e'
-//     }
-// }
+// https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/find-the-difference.py#L33
+pub struct Solution5 {}
+impl Solution5 {
+    pub fn find_the_difference(s: String, t: String) -> char {
+        let s_chars: HashSet<char> = s.chars().collect();
+        let mut t_chars: HashSet<char> = t.chars().collect();
+        s_chars.iter().for_each(|c| {
+            t_chars.remove(c);
+        });
+        t_chars.into_iter().collect::<Vec<char>>()[0]
+    }
+}
 
 // pub struct Solution6 {}
 // impl Solution6 {
@@ -61,5 +65,9 @@ mod tests {
             Solution3::find_the_difference("abcd".to_string(), "abcde".to_string()),
             'e'
         );
+        assert_eq!(
+            Solution5::find_the_difference("abcd".to_string(), "abcde".to_string()),
+            'e'
+        );
     }
 }

From 7753c9dcf488e4f45b0783cedf653b700ede79ab Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Wed, 31 Jul 2019 14:16:30 +0800
Subject: [PATCH 63/82] fix

---
 kamyu104/src/find_the_difference.rs | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/kamyu104/src/find_the_difference.rs b/kamyu104/src/find_the_difference.rs
index 4dc9cda..b3b79d6 100644
--- a/kamyu104/src/find_the_difference.rs
+++ b/kamyu104/src/find_the_difference.rs
@@ -17,14 +17,16 @@ use std::collections::HashSet;
 //     }
 // }
 
+// https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/find-the-difference.py#L18
 pub struct Solution3 {}
 impl Solution3 {
     pub fn find_the_difference(s: String, t: String) -> char {
         let s_chars: HashSet<char> = s.chars().collect();
-        let t_chars: HashSet<char> = t.chars().collect();
-        // or https://doc.rust-lang.org/std/collections/struct.HashSet.html#method.symmetric_difference
-        let diff: HashSet<&char> = t_chars.difference(&s_chars).collect(); 
-        *(diff.into_iter().collect::<Vec<&char>>()[0])
+        let mut t_chars: HashSet<char> = t.chars().collect();
+        s_chars.iter().for_each(|c| {
+            t_chars.remove(c);
+        });
+        t_chars.into_iter().collect::<Vec<char>>()[0]
     }
 }
 
@@ -40,11 +42,10 @@ pub struct Solution5 {}
 impl Solution5 {
     pub fn find_the_difference(s: String, t: String) -> char {
         let s_chars: HashSet<char> = s.chars().collect();
-        let mut t_chars: HashSet<char> = t.chars().collect();
-        s_chars.iter().for_each(|c| {
-            t_chars.remove(c);
-        });
-        t_chars.into_iter().collect::<Vec<char>>()[0]
+        let t_chars: HashSet<char> = t.chars().collect();
+        // or https://doc.rust-lang.org/std/collections/struct.HashSet.html#method.symmetric_difference
+        let diff: HashSet<&char> = t_chars.difference(&s_chars).collect();
+        *(diff.into_iter().collect::<Vec<&char>>()[0])
     }
 }
 

From 61a62cf7a124a433ca2a8a122fb4cb4e99d9d8a0 Mon Sep 17 00:00:00 2001
From: ChrisLinn <nanyishanshaoxiu@gmail.com>
Date: Wed, 31 Jul 2019 18:56:17 +0800
Subject: [PATCH 64/82] init test_read_binary_watch

---
 kamyu104/src/binary_watch.rs | 19 +++++++++++++++++++
 kamyu104/src/main.rs         |  1 +
 2 files changed, 20 insertions(+)
 create mode 100644 kamyu104/src/binary_watch.rs

diff --git a/kamyu104/src/binary_watch.rs b/kamyu104/src/binary_watch.rs
new file mode 100644
index 0000000..f3045ec
--- /dev/null
+++ b/kamyu104/src/binary_watch.rs
@@ -0,0 +1,19 @@
+pub struct Solution {}
+impl Solution {
+    // pub fn read_binary_watch(num: i32) -> Vec<String> {
+    //     vec![]
+    // }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_read_binary_watch() {
+        // assert_eq!(
+        //     Solution::read_binary_watch(1),
+        //     vec!["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]
+        // );
+    }
+}
diff --git a/kamyu104/src/main.rs b/kamyu104/src/main.rs
index 2d7e902..5e774cc 100644
--- a/kamyu104/src/main.rs
+++ b/kamyu104/src/main.rs
@@ -1,3 +1,4 @@
+mod binary_watch;
 mod bitwise_and_of_numbers_range;
 mod find_the_difference;
 mod maximum_product_of_word_lengths;

From 0f17beba9a5c799a10853b3243eb2f36015d2097 Mon Sep 17 00:00:00 2001
From: ChrisLinn <nanyishanshaoxiu@gmail.com>
Date: Wed, 31 Jul 2019 22:00:55 +0800
Subject: [PATCH 65/82] add testcases

---
 kamyu104/src/binary_watch.rs | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/kamyu104/src/binary_watch.rs b/kamyu104/src/binary_watch.rs
index f3045ec..3453231 100644
--- a/kamyu104/src/binary_watch.rs
+++ b/kamyu104/src/binary_watch.rs
@@ -1,8 +1,8 @@
 pub struct Solution {}
 impl Solution {
-    // pub fn read_binary_watch(num: i32) -> Vec<String> {
-    //     vec![]
-    // }
+    pub fn read_binary_watch(num: i32) -> Vec<String> {
+        vec![]
+    }
 }
 
 #[cfg(test)]
@@ -11,9 +11,19 @@ mod tests {
 
     #[test]
     fn test_read_binary_watch() {
-        // assert_eq!(
-        //     Solution::read_binary_watch(1),
-        //     vec!["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]
-        // );
+        assert_eq!(
+            Solution::read_binary_watch(1),
+            vec!["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]
+                .iter()
+                .map(|&x| String::from(x))
+                .collect::<Vec<String>>()
+        );
+        assert_eq!(
+            Solution::read_binary_watch(1),
+            vec!["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]
+                .iter()
+                .map(|&x| x.into())
+                .collect::<Vec<String>>()
+        );
     }
 }

From bdb75f5f8b31e0b2741a79063484e99724da52f8 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Thu, 1 Aug 2019 14:01:14 +0800
Subject: [PATCH 66/82] minor

---
 kamyu104/src/binary_watch.rs | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/kamyu104/src/binary_watch.rs b/kamyu104/src/binary_watch.rs
index 3453231..cdde695 100644
--- a/kamyu104/src/binary_watch.rs
+++ b/kamyu104/src/binary_watch.rs
@@ -1,7 +1,26 @@
 pub struct Solution {}
 impl Solution {
     pub fn read_binary_watch(num: i32) -> Vec<String> {
-        vec![]
+        // vec![]
+        let result: Vec<String> = Vec::new();
+        /*for (int h = 0; h < 12; ++h) {
+            for (int m = 0; m < 60; ++m) {
+                if (bit_count(h) + bit_count(m) == num) {
+                    const auto hour = to_string(h);
+                    const auto minute = m < 10 ? "0" + to_string(m) : to_string(m);
+                    result.emplace_back(hour + ":" + minute);
+                }
+            }
+        }*/
+        result
+    }
+
+    fn bit_count(bits: i32) -> i32 {
+        let mut count: i32 = 0;
+        // for (; bits; bits &= bits - 1) {
+        //     ++count;
+        // }
+        count
     }
 }
 

From 905afc72bb02d4f48c90891b58890438cca8d87c Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Thu, 1 Aug 2019 14:03:47 +0800
Subject: [PATCH 67/82] minor

---
 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 1857e98..1e6ee90 100644
--- a/README.md
+++ b/README.md
@@ -68,10 +68,10 @@ cargo test
 0371 | [Sum of Two Integers](https://leetcode.com/problems/sum-of-two-integers/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/sum-of-two-integers.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/sum-of-two-integers.py) <br>------</br> [Rust](./kamyu104/src/sum_of_two_integers.rs) | _O(1)_ | _O(1)_ | Easy | LintCode |
 0389 | [Find the Difference](https://leetcode.com/problems/find-the-difference/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/find-the-difference.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/find-the-difference.py) <br>------</br> [Rust](./kamyu104/src/find_the_difference.rs) | _O(n)_ | _O(1)_ | Easy | |
 0393 | [UTF-8 Validation](https://leetcode.com/problems/utf-8-validation/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/utf-8-validation.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/utf-8-validation.py) <br>------</br> [Rust](./kamyu104/src/utf_8_validation.rs) | _O(n)_ | _O(1)_ | Medium | |
+0401 | [Binary Watch](https://leetcode.com/problems/binary-watch/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/binary-watch.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/binary-watch.py) <br>------</br> [Rust](./kamyu104/src/binary_watch.rs) | _O(1)_ | _O(1)_ | Easy | |
 
 <!-- 
 
-0401 | [Binary Watch](https://leetcode.com/problems/binary-watch/) | [C++](./C++/binary-watch.cpp) [Python](./Python/binary-watch.py) | _O(1)_ | _O(1)_ | Easy | |
 0411 | [Minimum Unique Word Abbreviation](https://leetcode.com/problems/minimum-unique-word-abbreviation/) | [C++](./C++/minimum-unique-word-abbreviation.cpp) [Python](./Python/minimum-unique-word-abbreviation.py) | _O(2^n)_ | _O(n)_ | Hard | 🔒 |
 0421 | [Maximum XOR of Two Numbers in an Array](https://leetcode.com/problems/maximum-xor-of-two-numbers-in-an-array/) | [C++](./C++/maximum-xor-of-two-numbers-in-an-array.cpp) [Python](./Python/maximum-xor-of-two-numbers-in-an-array.py) | _O(n)_ | _O(n)_ | Medium ||
 0461 | [Hamming Distance](https://leetcode.com/problems/hamming-distance/) | [C++](./C++/hamming-distance.cpp) [Python](./Python/hamming-distance.py) | _O(1)_ | _O(1)_ | Easy ||

From 357b3c6324880f50adb46c0f7b6ddd8ed83b7420 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Thu, 1 Aug 2019 16:06:27 +0800
Subject: [PATCH 68/82] clean up

---
 kamyu104/src/binary_watch.rs | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/kamyu104/src/binary_watch.rs b/kamyu104/src/binary_watch.rs
index cdde695..5d53612 100644
--- a/kamyu104/src/binary_watch.rs
+++ b/kamyu104/src/binary_watch.rs
@@ -1,25 +1,24 @@
 pub struct Solution {}
 impl Solution {
     pub fn read_binary_watch(num: i32) -> Vec<String> {
-        // vec![]
-        let result: Vec<String> = Vec::new();
-        /*for (int h = 0; h < 12; ++h) {
-            for (int m = 0; m < 60; ++m) {
-                if (bit_count(h) + bit_count(m) == num) {
-                    const auto hour = to_string(h);
-                    const auto minute = m < 10 ? "0" + to_string(m) : to_string(m);
-                    result.emplace_back(hour + ":" + minute);
+        let mut result: Vec<String> = Vec::new();
+        (0..12).for_each(|h| {
+            (0..60).for_each(|m| {
+                if (Solution::bit_count(h) + Solution::bit_count(m)) == num {
+                    let elem = format!("{}:{:>02}", h, m);
+                    result.push(elem);
                 }
-            }
-        }*/
+            });
+        });
         result
     }
 
-    fn bit_count(bits: i32) -> i32 {
+    fn bit_count(mut bits: i32) -> i32 {
         let mut count: i32 = 0;
-        // for (; bits; bits &= bits - 1) {
-        //     ++count;
-        // }
+        while bits != 0 {
+            count += 1;
+            bits &= bits - 1;
+        }
         count
     }
 }
@@ -32,14 +31,15 @@ mod tests {
     fn test_read_binary_watch() {
         assert_eq!(
             Solution::read_binary_watch(1),
-            vec!["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]
+            // vec!["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]
+            vec!["0:01", "0:02", "0:04", "0:08", "0:16", "0:32", "1:00", "2:00", "4:00", "8:00"]
                 .iter()
                 .map(|&x| String::from(x))
                 .collect::<Vec<String>>()
         );
         assert_eq!(
             Solution::read_binary_watch(1),
-            vec!["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]
+            vec!["0:01", "0:02", "0:04", "0:08", "0:16", "0:32", "1:00", "2:00", "4:00", "8:00"]
                 .iter()
                 .map(|&x| x.into())
                 .collect::<Vec<String>>()

From 674c4e80706611caf4e33ba1859670f8a634e116 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Thu, 1 Aug 2019 16:37:08 +0800
Subject: [PATCH 69/82] wip

---
 kamyu104/src/binary_watch.rs | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/kamyu104/src/binary_watch.rs b/kamyu104/src/binary_watch.rs
index 5d53612..3ef83e8 100644
--- a/kamyu104/src/binary_watch.rs
+++ b/kamyu104/src/binary_watch.rs
@@ -1,3 +1,5 @@
+use std::collections::BTreeSet;
+
 pub struct Solution {}
 impl Solution {
     pub fn read_binary_watch(num: i32) -> Vec<String> {
@@ -5,7 +7,7 @@ impl Solution {
         (0..12).for_each(|h| {
             (0..60).for_each(|m| {
                 if (Solution::bit_count(h) + Solution::bit_count(m)) == num {
-                    let elem = format!("{}:{:>02}", h, m);
+                    let elem = format!("{}:{:02}", h, m);
                     result.push(elem);
                 }
             });
@@ -30,19 +32,22 @@ mod tests {
     #[test]
     fn test_read_binary_watch() {
         assert_eq!(
-            Solution::read_binary_watch(1),
-            // vec!["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]
-            vec!["0:01", "0:02", "0:04", "0:08", "0:16", "0:32", "1:00", "2:00", "4:00", "8:00"]
+            Solution::read_binary_watch(1)
+                .iter()
+                .collect::<BTreeSet<&String>>(),
+            vec!["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]
                 .iter()
                 .map(|&x| String::from(x))
-                .collect::<Vec<String>>()
+                .collect::<BTreeSet<String>>()
         );
         assert_eq!(
-            Solution::read_binary_watch(1),
-            vec!["0:01", "0:02", "0:04", "0:08", "0:16", "0:32", "1:00", "2:00", "4:00", "8:00"]
+            Solution::read_binary_watch(1)
+                .iter()
+                .collect::<BTreeSet<&String>>(),
+            vec!["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]
                 .iter()
                 .map(|&x| x.into())
-                .collect::<Vec<String>>()
+                .collect::<BTreeSet<String>>()
         );
     }
 }

From 06e1ec95290e8149bd4e651bff6036e18cb1154d Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Thu, 1 Aug 2019 17:07:08 +0800
Subject: [PATCH 70/82] fix

---
 kamyu104/src/binary_watch.rs | 17 ++++-------------
 1 file changed, 4 insertions(+), 13 deletions(-)

diff --git a/kamyu104/src/binary_watch.rs b/kamyu104/src/binary_watch.rs
index 3ef83e8..ddf94dd 100644
--- a/kamyu104/src/binary_watch.rs
+++ b/kamyu104/src/binary_watch.rs
@@ -33,20 +33,11 @@ mod tests {
     fn test_read_binary_watch() {
         assert_eq!(
             Solution::read_binary_watch(1)
-                .iter()
-                .collect::<BTreeSet<&String>>(),
+                .into_iter()
+                .collect::<BTreeSet<String>>(),
             vec!["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]
-                .iter()
-                .map(|&x| String::from(x))
-                .collect::<BTreeSet<String>>()
-        );
-        assert_eq!(
-            Solution::read_binary_watch(1)
-                .iter()
-                .collect::<BTreeSet<&String>>(),
-            vec!["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]
-                .iter()
-                .map(|&x| x.into())
+                .into_iter()
+                .map(String::from)
                 .collect::<BTreeSet<String>>()
         );
     }

From ddac1ec8eeef780295a753158dd615fb6f4883d0 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Thu, 1 Aug 2019 18:18:12 +0800
Subject: [PATCH 71/82] fix

---
 kamyu104/src/binary_watch.rs      |  6 ++++--
 kamyu104/src/single_number_iii.rs | 16 ++++++++++++++--
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/kamyu104/src/binary_watch.rs b/kamyu104/src/binary_watch.rs
index ddf94dd..764cd95 100644
--- a/kamyu104/src/binary_watch.rs
+++ b/kamyu104/src/binary_watch.rs
@@ -1,5 +1,8 @@
 use std::collections::BTreeSet;
 
+// Time:  O(1)
+// Space: O(1)
+
 pub struct Solution {}
 impl Solution {
     pub fn read_binary_watch(num: i32) -> Vec<String> {
@@ -7,8 +10,7 @@ impl Solution {
         (0..12).for_each(|h| {
             (0..60).for_each(|m| {
                 if (Solution::bit_count(h) + Solution::bit_count(m)) == num {
-                    let elem = format!("{}:{:02}", h, m);
-                    result.push(elem);
+                    result.push(format!("{}:{:02}", h, m));
                 }
             });
         });
diff --git a/kamyu104/src/single_number_iii.rs b/kamyu104/src/single_number_iii.rs
index 38b19c9..47b5ead 100644
--- a/kamyu104/src/single_number_iii.rs
+++ b/kamyu104/src/single_number_iii.rs
@@ -1,3 +1,5 @@
+use std::collections::BTreeSet;
+
 // Time:  O(n)
 // Space: O(1)
 
@@ -49,8 +51,18 @@ mod tests {
 
     #[test]
     fn test_single_number() {
-        assert_eq!(Solution1::single_number(vec![1, 2, 1, 3, 2, 5]), vec![5, 3]);
+        assert_eq!(
+            Solution1::single_number(vec![1, 2, 1, 3, 2, 5])
+                .into_iter()
+                .collect::<BTreeSet<i32>>(),
+            vec![3, 5].into_iter().collect::<BTreeSet<i32>>()
+        );
 
-        assert_eq!(Solution2::single_number(vec![1, 2, 1, 3, 2, 5]), vec![3, 5]);
+        assert_eq!(
+            Solution2::single_number(vec![1, 2, 1, 3, 2, 5])
+                .into_iter()
+                .collect::<BTreeSet<i32>>(),
+            vec![3, 5].into_iter().collect::<BTreeSet<i32>>()
+        );
     }
 }

From 63c8b96d026cc213de3867948f36ea0cc41192d9 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Thu, 1 Aug 2019 18:24:17 +0800
Subject: [PATCH 72/82] init maximum_xor_of_two_numbers_in_an_array

---
 README.md                                              | 4 ++--
 kamyu104/src/main.rs                                   | 1 +
 kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs | 1 +
 3 files changed, 4 insertions(+), 2 deletions(-)
 create mode 100644 kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs

diff --git a/README.md b/README.md
index 1e6ee90..ad6fcc7 100644
--- a/README.md
+++ b/README.md
@@ -69,11 +69,11 @@ cargo test
 0389 | [Find the Difference](https://leetcode.com/problems/find-the-difference/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/find-the-difference.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/find-the-difference.py) <br>------</br> [Rust](./kamyu104/src/find_the_difference.rs) | _O(n)_ | _O(1)_ | Easy | |
 0393 | [UTF-8 Validation](https://leetcode.com/problems/utf-8-validation/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/utf-8-validation.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/utf-8-validation.py) <br>------</br> [Rust](./kamyu104/src/utf_8_validation.rs) | _O(n)_ | _O(1)_ | Medium | |
 0401 | [Binary Watch](https://leetcode.com/problems/binary-watch/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/binary-watch.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/binary-watch.py) <br>------</br> [Rust](./kamyu104/src/binary_watch.rs) | _O(1)_ | _O(1)_ | Easy | |
+0411 | [~~Minimum Unique Word Abbreviation~~](https://leetcode.com/problems/minimum-unique-word-abbreviation/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/minimum-unique-word-abbreviation.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/minimum-unique-word-abbreviation.py) | _O(2^n)_ | _O(n)_ | Hard | 🔒 |
+0421 | [Maximum XOR of Two Numbers in an Array](https://leetcode.com/problems/maximum-xor-of-two-numbers-in-an-array/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/maximum-xor-of-two-numbers-in-an-array.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-xor-of-two-numbers-in-an-array.py) <br>------</br> [Rust](./kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs) | _O(n)_ | _O(n)_ | Medium ||
 
 <!-- 
 
-0411 | [Minimum Unique Word Abbreviation](https://leetcode.com/problems/minimum-unique-word-abbreviation/) | [C++](./C++/minimum-unique-word-abbreviation.cpp) [Python](./Python/minimum-unique-word-abbreviation.py) | _O(2^n)_ | _O(n)_ | Hard | 🔒 |
-0421 | [Maximum XOR of Two Numbers in an Array](https://leetcode.com/problems/maximum-xor-of-two-numbers-in-an-array/) | [C++](./C++/maximum-xor-of-two-numbers-in-an-array.cpp) [Python](./Python/maximum-xor-of-two-numbers-in-an-array.py) | _O(n)_ | _O(n)_ | Medium ||
 0461 | [Hamming Distance](https://leetcode.com/problems/hamming-distance/) | [C++](./C++/hamming-distance.cpp) [Python](./Python/hamming-distance.py) | _O(1)_ | _O(1)_ | Easy ||
 0462 | [Minimum Moves to Equal Array Elements II](https://leetcode.com/problems/minimum-moves-to-equal-array-elements-ii/) | [C++](./C++/minimum-moves-to-equal-array-elements-ii.cpp) [Python](./Python/minimum-moves-to-equal-array-elements-ii.py) | _O(n)_  on average | _O(1)_ | Medium ||
 0477 | [Total Hamming Distance](https://leetcode.com/problems/total-hamming-distance/) | [C++](./C++/total-hamming-distance.cpp) [Python](./Python/total-hamming-distance.py) | _O(n)_ | _O(1)_ | Medium ||
diff --git a/kamyu104/src/main.rs b/kamyu104/src/main.rs
index 5e774cc..be1ad38 100644
--- a/kamyu104/src/main.rs
+++ b/kamyu104/src/main.rs
@@ -2,6 +2,7 @@ mod binary_watch;
 mod bitwise_and_of_numbers_range;
 mod find_the_difference;
 mod maximum_product_of_word_lengths;
+mod maximum_xor_of_two_numbers_in_an_array;
 mod missing_number;
 mod number_of_1_bits;
 mod power_of_four;
diff --git a/kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs b/kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs
new file mode 100644
index 0000000..8b13789
--- /dev/null
+++ b/kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs
@@ -0,0 +1 @@
+

From fecae2ef066832ac09047edb87e985adf6d8aa1c Mon Sep 17 00:00:00 2001
From: ChrisLinn <nanyishanshaoxiu@gmail.com>
Date: Thu, 1 Aug 2019 20:24:19 +0800
Subject: [PATCH 73/82] add

---
 kamyu104/src/binary_watch.rs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kamyu104/src/binary_watch.rs b/kamyu104/src/binary_watch.rs
index 764cd95..3ad132f 100644
--- a/kamyu104/src/binary_watch.rs
+++ b/kamyu104/src/binary_watch.rs
@@ -42,5 +42,14 @@ mod tests {
                 .map(String::from)
                 .collect::<BTreeSet<String>>()
         );
+        assert_eq!(
+            Solution::read_binary_watch(1)
+                .into_iter()
+                .collect::<BTreeSet<String>>(),
+            vec!["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]
+                .into_iter()
+                .map(Into::into)
+                .collect::<BTreeSet<String>>()
+        );
     }
 }

From 39587a17b325eb5ea7aa421555fd27ca9e6f83dd Mon Sep 17 00:00:00 2001
From: ChrisLinn <nanyishanshaoxiu@gmail.com>
Date: Thu, 1 Aug 2019 20:27:13 +0800
Subject: [PATCH 74/82] add

---
 .../src/maximum_xor_of_two_numbers_in_an_array.rs | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs b/kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs
index 8b13789..5f3c8d6 100644
--- a/kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs
+++ b/kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs
@@ -1 +1,16 @@
+pub struct Solution {}
+impl Solution {
+    pub fn find_maximum_xor(nums: Vec<i32>) -> i32 {
+        0
+    }
+}
 
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_find_maximum_xor() {
+        assert_eq!(Solution::find_maximum_xor(vec![3, 10, 5, 25, 2, 8]), 28);
+    }
+}

From c1fc403606d05f196982aaa249c15f0824bebfb7 Mon Sep 17 00:00:00 2001
From: ChrisLinn <nanyishanshaoxiu@gmail.com>
Date: Fri, 2 Aug 2019 06:41:46 +0800
Subject: [PATCH 75/82] fix

---
 .../maximum_xor_of_two_numbers_in_an_array.rs | 21 ++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs b/kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs
index 5f3c8d6..d3c106c 100644
--- a/kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs
+++ b/kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs
@@ -1,7 +1,26 @@
+use std::collections::HashSet;
+  
+// Time:  O(n)
+// Space: O(n)
+
 pub struct Solution {}
 impl Solution {
     pub fn find_maximum_xor(nums: Vec<i32>) -> i32 {
-        0
+        let mut result: i32 = 0;
+        for i in (0..32).rev() {
+            result <<= 1;
+            let mut prefixes: HashSet<i32> = HashSet::new();
+            for n in nums.clone() {
+                prefixes.insert(n >> i);
+            }
+            for p in prefixes.clone() {
+                if prefixes.contains(&((result | 1) ^ p)) {
+                    result += 1;
+                    break;
+                }
+            }
+        }
+        result
     }
 }
 

From fbcbd6eb6f7cdd1f991304dc75c520796588511f Mon Sep 17 00:00:00 2001
From: ChrisLinn <nanyishanshaoxiu@gmail.com>
Date: Fri, 2 Aug 2019 06:48:19 +0800
Subject: [PATCH 76/82] fix

---
 kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs b/kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs
index d3c106c..500b593 100644
--- a/kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs
+++ b/kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs
@@ -1,5 +1,5 @@
 use std::collections::HashSet;
-  
+
 // Time:  O(n)
 // Space: O(n)
 

From 8fde83cbcd7ad79e1ecc22989e2ba53cde60f1be Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Fri, 2 Aug 2019 15:30:31 +0800
Subject: [PATCH 77/82] init hamming_distance

---
 README.md                        | 2 +-
 kamyu104/src/hamming_distance.rs | 1 +
 kamyu104/src/main.rs             | 1 +
 3 files changed, 3 insertions(+), 1 deletion(-)
 create mode 100644 kamyu104/src/hamming_distance.rs

diff --git a/README.md b/README.md
index ad6fcc7..bec5124 100644
--- a/README.md
+++ b/README.md
@@ -71,10 +71,10 @@ cargo test
 0401 | [Binary Watch](https://leetcode.com/problems/binary-watch/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/binary-watch.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/binary-watch.py) <br>------</br> [Rust](./kamyu104/src/binary_watch.rs) | _O(1)_ | _O(1)_ | Easy | |
 0411 | [~~Minimum Unique Word Abbreviation~~](https://leetcode.com/problems/minimum-unique-word-abbreviation/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/minimum-unique-word-abbreviation.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/minimum-unique-word-abbreviation.py) | _O(2^n)_ | _O(n)_ | Hard | 🔒 |
 0421 | [Maximum XOR of Two Numbers in an Array](https://leetcode.com/problems/maximum-xor-of-two-numbers-in-an-array/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/maximum-xor-of-two-numbers-in-an-array.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-xor-of-two-numbers-in-an-array.py) <br>------</br> [Rust](./kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs) | _O(n)_ | _O(n)_ | Medium ||
+0461 | [Hamming Distance](https://leetcode.com/problems/hamming-distance/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/hamming-distance.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/hamming-distance.py) <br>------</br> [Rust](./kamyu104/src/hamming_distance.rs) | _O(1)_ | _O(1)_ | Easy ||
 
 <!-- 
 
-0461 | [Hamming Distance](https://leetcode.com/problems/hamming-distance/) | [C++](./C++/hamming-distance.cpp) [Python](./Python/hamming-distance.py) | _O(1)_ | _O(1)_ | Easy ||
 0462 | [Minimum Moves to Equal Array Elements II](https://leetcode.com/problems/minimum-moves-to-equal-array-elements-ii/) | [C++](./C++/minimum-moves-to-equal-array-elements-ii.cpp) [Python](./Python/minimum-moves-to-equal-array-elements-ii.py) | _O(n)_  on average | _O(1)_ | Medium ||
 0477 | [Total Hamming Distance](https://leetcode.com/problems/total-hamming-distance/) | [C++](./C++/total-hamming-distance.cpp) [Python](./Python/total-hamming-distance.py) | _O(n)_ | _O(1)_ | Medium ||
 0645 | [Set Mismatch](https://leetcode.com/problems/set-mismatch/) | [C++](./C++/set-mismatch.cpp) [Python](./Python/set-mismatch.py) | _O(n)_ | _O(1)_ | Easy ||
diff --git a/kamyu104/src/hamming_distance.rs b/kamyu104/src/hamming_distance.rs
new file mode 100644
index 0000000..8b13789
--- /dev/null
+++ b/kamyu104/src/hamming_distance.rs
@@ -0,0 +1 @@
+
diff --git a/kamyu104/src/main.rs b/kamyu104/src/main.rs
index be1ad38..5420d3f 100644
--- a/kamyu104/src/main.rs
+++ b/kamyu104/src/main.rs
@@ -1,6 +1,7 @@
 mod binary_watch;
 mod bitwise_and_of_numbers_range;
 mod find_the_difference;
+mod hamming_distance;
 mod maximum_product_of_word_lengths;
 mod maximum_xor_of_two_numbers_in_an_array;
 mod missing_number;

From 8a134b03a8d1bb18d3e73f7dffaa756634e2bb6b Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Fri, 2 Aug 2019 15:33:20 +0800
Subject: [PATCH 78/82] add

---
 kamyu104/src/hamming_distance.rs | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/kamyu104/src/hamming_distance.rs b/kamyu104/src/hamming_distance.rs
index 8b13789..4bbf05b 100644
--- a/kamyu104/src/hamming_distance.rs
+++ b/kamyu104/src/hamming_distance.rs
@@ -1 +1,19 @@
+// Time:  O(1)
+// Space: O(1)
+pub struct Solution {}
+impl Solution {
+    pub fn hamming_distance(x: i32, y: i32) -> i32 {
+        2
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_hamming_distance() {
+        assert_eq!(Solution::hamming_distance(1, 4), 2);
+    }
+}
 

From 018cd5ca9480e688aa7296cab8c9b4802b681611 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Fri, 2 Aug 2019 15:43:15 +0800
Subject: [PATCH 79/82] fix

---
 kamyu104/src/hamming_distance.rs | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/kamyu104/src/hamming_distance.rs b/kamyu104/src/hamming_distance.rs
index 4bbf05b..4be42f1 100644
--- a/kamyu104/src/hamming_distance.rs
+++ b/kamyu104/src/hamming_distance.rs
@@ -3,7 +3,13 @@
 pub struct Solution {}
 impl Solution {
     pub fn hamming_distance(x: i32, y: i32) -> i32 {
-        2
+        let mut distance: i32 = 0;
+        let mut z: i32 = x ^ y;
+        while z != 0 {
+            distance += 1;
+            z &= z - 1;
+        }
+        distance
     }
 }
 
@@ -16,4 +22,3 @@ mod tests {
         assert_eq!(Solution::hamming_distance(1, 4), 2);
     }
 }
-

From 98d860b05e4a3bf60e5821f16dd68eb8abd76fa9 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Fri, 2 Aug 2019 15:45:22 +0800
Subject: [PATCH 80/82] add 2

---
 kamyu104/src/hamming_distance.rs | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/kamyu104/src/hamming_distance.rs b/kamyu104/src/hamming_distance.rs
index 4be42f1..6868b21 100644
--- a/kamyu104/src/hamming_distance.rs
+++ b/kamyu104/src/hamming_distance.rs
@@ -1,7 +1,8 @@
 // Time:  O(1)
 // Space: O(1)
-pub struct Solution {}
-impl Solution {
+
+pub struct Solution1 {}
+impl Solution1 {
     pub fn hamming_distance(x: i32, y: i32) -> i32 {
         let mut distance: i32 = 0;
         let mut z: i32 = x ^ y;
@@ -13,12 +14,19 @@ impl Solution {
     }
 }
 
+pub struct Solution2 {}
+impl Solution2 {
+    pub fn hamming_distance(x: i32, y: i32) -> i32 {
+        2
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
     #[test]
     fn test_hamming_distance() {
-        assert_eq!(Solution::hamming_distance(1, 4), 2);
+        assert_eq!(Solution1::hamming_distance(1, 4), 2);
     }
 }

From 468e52d981ee4093e09a2efd5a48239aefcde5f2 Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Fri, 2 Aug 2019 16:24:23 +0800
Subject: [PATCH 81/82] fix

---
 kamyu104/src/hamming_distance.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kamyu104/src/hamming_distance.rs b/kamyu104/src/hamming_distance.rs
index 6868b21..7cebb5a 100644
--- a/kamyu104/src/hamming_distance.rs
+++ b/kamyu104/src/hamming_distance.rs
@@ -17,7 +17,8 @@ impl Solution1 {
 pub struct Solution2 {}
 impl Solution2 {
     pub fn hamming_distance(x: i32, y: i32) -> i32 {
-        2
+        let z = format!("{:b}", x ^ y);
+        z.chars().filter(|&c| c == '1').count() as i32
     }
 }
 
@@ -28,5 +29,6 @@ mod tests {
     #[test]
     fn test_hamming_distance() {
         assert_eq!(Solution1::hamming_distance(1, 4), 2);
+        assert_eq!(Solution2::hamming_distance(1, 4), 2);
     }
 }

From 4c10ad88903271cab2a03788d2d1c3e39c8cf33d Mon Sep 17 00:00:00 2001
From: HAOYUatHZ <haoyu@protonmail.com>
Date: Fri, 2 Aug 2019 18:22:29 +0800
Subject: [PATCH 82/82] add

---
 README.md                                     |  2 +-
 kamyu104/src/main.rs                          |  1 +
 ...inimum_moves_to_equal_array_elements_ii.rs | 20 +++++++++++++++++++
 3 files changed, 22 insertions(+), 1 deletion(-)
 create mode 100644 kamyu104/src/minimum_moves_to_equal_array_elements_ii.rs

diff --git a/README.md b/README.md
index a1514b5..3076d13 100644
--- a/README.md
+++ b/README.md
@@ -72,6 +72,7 @@ cargo test
 0411 | [~~Minimum Unique Word Abbreviation~~](https://leetcode.com/problems/minimum-unique-word-abbreviation/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/minimum-unique-word-abbreviation.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/minimum-unique-word-abbreviation.py) | _O(2^n)_ | _O(n)_ | Hard | 🔒 |
 0421 | [Maximum XOR of Two Numbers in an Array](https://leetcode.com/problems/maximum-xor-of-two-numbers-in-an-array/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/maximum-xor-of-two-numbers-in-an-array.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/maximum-xor-of-two-numbers-in-an-array.py) <br>------</br> [Rust](./kamyu104/src/maximum_xor_of_two_numbers_in_an_array.rs) | _O(n)_ | _O(n)_ | Medium ||
 0461 | [Hamming Distance](https://leetcode.com/problems/hamming-distance/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/hamming-distance.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/hamming-distance.py) <br>------</br> [Rust](./kamyu104/src/hamming_distance.rs) | _O(1)_ | _O(1)_ | Easy ||
+0462 | [Minimum Moves to Equal Array Elements II](https://leetcode.com/problems/minimum-moves-to-equal-array-elements-ii/) | [C++](https://github.com/kamyu104/LeetCode-Solutions/blob/master/C++/minimum-moves-to-equal-array-elements-ii.cpp) [Python](https://github.com/kamyu104/LeetCode-Solutions/blob/master/Python/minimum-moves-to-equal-array-elements-ii.py) <br>------</br> [Rust](./kamyu104/src/minimum_moves_to_equal_array_elements_ii.rs) | _O(n)_  on average | _O(1)_ | Medium ||
 
 <!-- 
 
@@ -79,7 +80,6 @@ cargo test
 
 <!-- 
 
-0462 | [Minimum Moves to Equal Array Elements II](https://leetcode.com/problems/minimum-moves-to-equal-array-elements-ii/) | [C++](./C++/minimum-moves-to-equal-array-elements-ii.cpp) [Python](./Python/minimum-moves-to-equal-array-elements-ii.py) | _O(n)_  on average | _O(1)_ | Medium ||
 0477 | [Total Hamming Distance](https://leetcode.com/problems/total-hamming-distance/) | [C++](./C++/total-hamming-distance.cpp) [Python](./Python/total-hamming-distance.py) | _O(n)_ | _O(1)_ | Medium ||
 0645 | [Set Mismatch](https://leetcode.com/problems/set-mismatch/) | [C++](./C++/set-mismatch.cpp) [Python](./Python/set-mismatch.py) | _O(n)_ | _O(1)_ | Easy ||
 0693 | [Binary Number with Alternating Bits](https://leetcode.com/problems/binary-number-with-alternating-bits/) | [C++](./C++/binary-number-with-alternating-bits.cpp) [Python](./Python/binary-number-with-alternating-bits.py) | _O(1)_ | _O(1)_ | Easy ||
diff --git a/kamyu104/src/main.rs b/kamyu104/src/main.rs
index 5420d3f..7ea90ae 100644
--- a/kamyu104/src/main.rs
+++ b/kamyu104/src/main.rs
@@ -4,6 +4,7 @@ mod find_the_difference;
 mod hamming_distance;
 mod maximum_product_of_word_lengths;
 mod maximum_xor_of_two_numbers_in_an_array;
+mod minimum_moves_to_equal_array_elements_ii;
 mod missing_number;
 mod number_of_1_bits;
 mod power_of_four;
diff --git a/kamyu104/src/minimum_moves_to_equal_array_elements_ii.rs b/kamyu104/src/minimum_moves_to_equal_array_elements_ii.rs
new file mode 100644
index 0000000..f003b8c
--- /dev/null
+++ b/kamyu104/src/minimum_moves_to_equal_array_elements_ii.rs
@@ -0,0 +1,20 @@
+// Time:  O(n) on average
+// Space: O(1)
+
+// Quick select solution.
+pub struct Solution {}
+impl Solution {
+    pub fn min_moves2(nums: Vec<i32>) -> i32 {
+        2
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_min_moves2() {
+        assert_eq!(Solution::min_moves2(vec![1, 2, 3]), 2);
+    }
+}