add missing_number (#13)

* init missing_number

* add

* add more

* add missing_number

* add mroe

* add sol4

* add sol3

* udpate readme

Author: 0xmountaintop

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 |

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;

kamyu104/src/missing_number.rs

@@ -0,0 +1,72 @@
+// Time:  O(n)
+// Space: O(1)
+pub struct Solution1 {}
+impl Solution1 {
+    pub fn missing_number(nums: Vec<i32>) -> i32 {
+        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
+//     }
+// }
+
+// Time:  O(n)
+// Space: O(1)
+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)
+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 {
+    use super::*;
+
+    #[test]
+    fn test_missing_number() {
+        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
+        // );
+
+        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!(
+            Solution4::missing_number(vec![9, 6, 4, 2, 3, 5, 7, 0, 1]),
+            8
+        );
+    }
+}