409. Longest Palindrome

Given a string which consists of lowercase or uppercase letters, find the length of the longest palindromes that can be built with those letters.

This is case sensitive, for example "Aa" is not considered a palindrome here.

Note:
Assume the length of given string will not exceed 1,010.

Example:

Input:
"abccccdd"

Output:
7

Explanation:
One longest palindrome that can be built is "dccaccd", whose length is 7.


从字符串中找出一些字母组成回文串，要求这个回文串最长

C++（9ms）：

class Solution {
public:
    int longestPalindrome(string s) {
        vector<int> Map(128,0) ;
        for(char c : s){
            Map[c - 'A']++ ;
        }
        int res = 0 ;
        for(int i = 0 ; i < Map.size() ; i++){
            res += Map[i]/2*2 ; 
        }
        return res == s.length()?res:res+1 ;
    }
};

Java(22ms):

class Solution {
    public int longestPalindrome(String s) {
        HashMap<Character,Integer> Map = new HashMap() ;
        int res = 0 ;
        for (char c : s.toCharArray()){
            Map.put(c , Map.getOrDefault(c,0) + 1) ;
        }
        for (char c : Map.keySet()){
            res += Map.get(c)/2*2 ;
        }
        return res == s.length()?res:res+1 ;
    }
}