Solution.java

class Solution {
    public int longestPalindrome(String s) {
        int[] cnt = new int[128];
        for (int i = 0; i < s.length(); ++i) {
            ++cnt[s.charAt(i)];
        }
        int ans = 0;
        for (int v : cnt) {
            ans += v - (v & 1);
            if (ans % 2 == 0 && v % 2 == 1) {
                ++ans;
            }
        }
        return ans;
    }
}