add max_product (#18)

Author: 0xmountaintop

kamyu104/src/maximum_product_of_word_lengths.rs

@@ -1,5 +1,63 @@
-pub struct Solution {}
-impl Solution {
+// 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 {
+        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 {
+        let mut sorted_words = words.clone();
+        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() {
+                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 {
+            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
+    }
+}
+
+
+// # 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
     }
@@ -11,8 +69,32 @@ 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_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
+        );
     }
-}
+}