Longest Palindrome

leetcode-409.cpp

class Solution {
public:
    int longestPalindrome(string s) {
        unordered_map<int, int> mp;

        for (char& ch : s)
            mp[ch]++;

        bool odd_cnt = false;
        int res = 0;

        for (auto& it : mp) {
            if (it.second % 2 == 0)
                res += it.second;
            else {
                odd_cnt = true;
                res += it.second - 1;
            }
        }
        if (odd_cnt)
            return res += 1;

        return res;
    }
};