https://leetcode.com/problems/longest-palindrome/

longestPalindrome.java

public class Solution {
    public int longestPalindrome(String s) {
        int m = 0;
        int n = 0;
        Map<Character, Integer> cache = new HashMap<Character, Integer>();
        char[] sc = s.toCharArray();
        for(char c : sc){
            if(cache.get(c) != null){
               cache.put(c, cache.get(c) + 1); 
            } else {
				cache.put(c, 1);
			}
        }
        for(char c : cache.keySet()){
            int count = cache.get(c);
            m += count / 2;
            if(count%2 == 1){
                ++n;
            }
        }
        if(n > 1){
            n = 1;  
        } 
        
        return m*2+n;
    }
}