409. Longest Palindrome

class Solution {private:    bool static compare(int a,int b)    {        return a>b;    }public:    int longestPalindrome(string s) {        map<char ,int > m;        for(int i=0;i<s.size();i++)        {            m[s[i]]++;        }        int rest=0;        vector<int> v;        for(map<char,int>::iterator it=m.begin();it!=m.end();it++)        {            if(it->second%2==0)            {                rest+=it->second;            }            else            {                v.push_back(it->second);            }        }        sort(v.begin(),v.end(),compare);        if(v.size()>0)        {            rest+=v[0];        }        for(int i=1;i<v.size();i++)        {            if(v[i]>1)                rest+=(v[i]-1);            else                break;        }        return rest;    }};