1542. Find Longest Awesome Substring: AC

Author: tan-wei

src/solution/mod.rs

@@ -1163,3 +1163,4 @@ mod s1537_get_the_maximum_score;
 mod s1539_kth_missing_positive_number;
 mod s1540_can_convert_string_in_k_moves;
 mod s1541_minimum_insertions_to_balance_a_parentheses_string;
+mod s1542_find_longest_awesome_substring;

src/solution/s1542_find_longest_awesome_substring.rs

@@ -0,0 +1,96 @@
+/**
+ * [1542] Find Longest Awesome Substring
+ *
+ * You are given a string s. An awesome substring is a non-empty substring of s such that we can make any number of swaps in order to make it a palindrome.
+ * Return the length of the maximum length awesome substring of s.
+ *  
+ * Example 1:
+ *
+ * Input: s = "3242415"
+ * Output: 5
+ * Explanation: "24241" is the longest awesome substring, we can form the palindrome "24142" with some swaps.
+ *
+ * Example 2:
+ *
+ * Input: s = "12345678"
+ * Output: 1
+ *
+ * Example 3:
+ *
+ * Input: s = "213123"
+ * Output: 6
+ * Explanation: "213123" is the longest awesome substring, we can form the palindrome "231132" with some swaps.
+ *
+ *  
+ * Constraints:
+ *
+ * 	1 <= s.length <= 10^5
+ * 	s consists only of digits.
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/find-longest-awesome-substring/
+// discuss: https://leetcode.com/problems/find-longest-awesome-substring/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn longest_awesome(s: String) -> i32 {
+        let mut map = std::collections::HashMap::new();
+        let mut mask = 0;
+        let mut result = 0;
+
+        map.insert(0, -1);
+
+        for (i, c) in s.bytes().enumerate() {
+            mask ^= 1 << (c - b'0');
+            if let Some(&j) = map.get(&mask) {
+                result = result.max(i as i32 - j);
+            }
+            for k in 0..10 {
+                let mask2 = mask ^ (1 << k);
+                if let Some(&j) = map.get(&mask2) {
+                    result = result.max(i as i32 - j);
+                }
+            }
+            map.entry(mask).or_insert(i as i32);
+        }
+
+        result
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_1542_example_1() {
+        let s = "3242415".to_string();
+
+        let result = 5;
+
+        assert_eq!(Solution::longest_awesome(s), result);
+    }
+
+    #[test]
+    fn test_1542_example_2() {
+        let s = "12345678".to_string();
+
+        let result = 1;
+
+        assert_eq!(Solution::longest_awesome(s), result);
+    }
+
+    #[test]
+    fn test_1542_example_3() {
+        let s = "213123".to_string();
+
+        let result = 6;
+
+        assert_eq!(Solution::longest_awesome(s), result);
+    }
+}