longest-palindrome.js

/**
 * Longest Palindrome
 *
 * Given a string which consists of lowercase or uppercase letters,
 * find the length of the longest palindromes that can be built with those letters.
 *
 * This is case sensitive, for example "Aa" is not considered a palindrome here.
 *
 * Note:
 * Assume the length of given string will not exceed 1,010.
 *
 * Example:
 *
 * Input:
 * "abccccdd"
 *
 * Output:
 * 7
 *
 * Explanation:
 * One longest palindrome that can be built is "dccaccd", whose length is 7.
 */

/**
 * @param {string} s
 * @return {number}
 */
const longestPalindrome = s => {
  const set = new Set();
  let count = 0; // count of pair

  for (let c of s) {
    if (set.has(c)) {
      set.delete(c);
      count++; // found a pair
    } else {
      set.add(c);
    }
  }

  return set.size > 0 ? 2 * count + 1 : 2 * count;
};

export { longestPalindrome };