409. Longest Palindrome

Javascript

/**
 * @param {string} s
 * @return {number}
 */
var longestPalindrome = function(s) {
    var count=0;
    var m=s.split("");
    m.sort();
    for(var i=0;i<m.length-1;i++)
    {
        if(m[i]===m[i+1])
        {
            count+=2;
            m.splice(i,2);
            i--;
        }
    }
    if(m.length>0) count++;
    return count;
};

优解，用了hash

public class Solution {
    public int longestPalindrome(String s) {
        if(s==null || s.length()==0) return 0;
        HashSet<Character> hs = new HashSet<Character>();
        int count = 0;
        for(int i=0; i<s.length(); i++){
            if(hs.contains(s.charAt(i))){
                hs.remove(s.charAt(i));
                count++;
            }else{
                hs.add(s.charAt(i));
            }
        }
        if(!hs.isEmpty()) return count*2+1;
        return count*2;
}
}