627. Longest Palindrome

  1. class Solution {
  2. public:
  3.     /**
  4.      * @param s: a string which consists of lowercase or uppercase letters
  5.      * @return: the length of the longest palindromes that can be built
  6.      */
  7.     int longestPalindrome(string &s) {
  8.         // write your code here
  9.         int res = 0;
  10.         unordered_set <int> set;
  11.         for (int i = 0; i < s.size(); i ++){
  12.             if (set.count(s[i]) == 0)
  13.                 set.insert(s[i]);
  14.             else{
  15.                 set.erase(s[i]);
  16.                 res += 2;
  17.             }
  18.         }
  19.         if (!set.empty()){
  20.             res ++;
  21.         }
  22.         return res;
  23.     }
  24. };