leetcode 409 Longest Palindrome

class Solution {
public:
    int longestPalindrome(string s) {
        int re=0;
        vector<int> vec(58,0);
        for(auto& c:s) {
            ++vec[c-'A'];
        }
        for(auto&t: vec) {
            re+=t/2*2;
            if(re%2==0&&t%2==1) ++re;
        }
        return re;
    }
};