solutions/1328-break-a-palindrome.js

/**
 * 1328. Break a Palindrome
 * https://leetcode.com/problems/break-a-palindrome/
 * Difficulty: Medium
 *
 * Given a palindromic string of lowercase English letters palindrome, replace exactly one
 * character with any lowercase English letter so that the resulting string is not a palindrome
 * and that it is the lexicographically smallest one possible.
 *
 * Return the resulting string. If there is no way to replace a character to make it not a
 * palindrome, return an empty string.
 *
 * A string a is lexicographically smaller than a string b (of the same length) if in the first
 * position where a and b differ, a has a character strictly smaller than the corresponding
 * character in b. For example, "abcc" is lexicographically smaller than "abcd" because the
 * first position they differ is at the fourth character, and 'c' is smaller than 'd'.
 */

/**
 * @param {string} palindrome
 * @return {string}
 */
var breakPalindrome = function(palindrome) {
  if (palindrome.length === 1) return '';

  const chars = palindrome.split('');

  for (let i = 0; i < Math.floor(chars.length / 2); i++) {
    if (chars[i] !== 'a') {
      chars[i] = 'a';
      return chars.join('');
    }
  }

  chars[chars.length - 1] = 'b';
  return chars.join('');
};