20231213 Finished

src/solution/mod.rs

@@ -1,3 +1,4 @@
 mod s0001_two_sum;
 mod s0009_palindrome_number;
 mod s0020_valid_parentheses;
+mod s2697_lexicographically_smallest_palindrome;

src/solution/s2697_lexicographically_smallest_palindrome.rs

@@ -0,0 +1,79 @@
+/**
+ * [2697] Lexicographically Smallest Palindrome
+ *
+ * You are given a string <code node="[object Object]">s consisting of lowercase English letters, and you are allowed to perform operations on it. In one operation, you can replace a character in <code node="[object Object]">s with another lowercase English letter.
+ * Your task is to make <code node="[object Object]">s a palindrome with the minimum number of operations possible. If there are multiple palindromes that can be <meta charset="utf-8" />made using the minimum number of operations, <meta charset="utf-8" />make the lexicographically smallest one.
+ * A string a is lexicographically smaller than a string b (of the same length) if in the first position where a and b differ, string a has a letter that appears earlier in the alphabet than the corresponding letter in b.
+ * Return the resulting palindrome string.
+ *  
+ * <strong class="example">Example 1:
+ *
+ * Input: s = "egcfe"
+ * Output: "efcfe"
+ * Explanation: The minimum number of operations to make "egcfe" a palindrome is 1, and the lexicographically smallest palindrome string we can get by modifying one character is "efcfe", by changing 'g'.
+ *
+ * <strong class="example">Example 2:
+ *
+ * Input: s = "abcd"
+ * Output: "abba"
+ * Explanation: The minimum number of operations to make "abcd" a palindrome is 2, and the lexicographically smallest palindrome string we can get by modifying two characters is "abba".
+ *
+ * <strong class="example">Example 3:
+ *
+ * Input: s = "seven"
+ * Output: "neven"
+ * Explanation: The minimum number of operations to make "seven" a palindrome is 1, and the lexicographically smallest palindrome string we can get by modifying one character is "neven".
+ *
+ *  
+ * Constraints:
+ *
+ * 	1 <= s.length <= 1000
+ * 	s consists of only lowercase English letters.
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.cn/problems/lexicographically-smallest-palindrome/
+// discuss: https://leetcode.cn/problems/lexicographically-smallest-palindrome/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+use std::cmp::min;
+impl Solution {
+    pub fn make_smallest_palindrome(s: String) -> String {
+        let mut result : Vec<u8> = s.bytes().collect();
+        let mut left = 0;
+        let mut right = result.len() - 1;
+
+        while left < right {
+            if result[left] != result[right] {
+                let value = min(result[left], result[right]);
+
+                result[left] = value;
+                result[right] = value;
+            }
+
+            left = left + 1;
+            right = right - 1;
+        }
+
+        String::from_utf8(result).unwrap()
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_2697() {
+        assert_eq!(String::from("efcfe"),
+                   Solution::make_smallest_palindrome(String::from("egcfe")));
+        assert_eq!(String::from("abba"),
+                   Solution::make_smallest_palindrome(String::from("abcd")));
+        assert_eq!(String::from("neven"),
+                   Solution::make_smallest_palindrome(String::from("seven")));
+    }
+}