451. Sort Characters By Frequency

pair排序

class Solution {public:    static bool cmp(pair<char,int> &a ,pair<char,int> &b )    {        if(a.second>b.second)            return true;        else            return false;    }    string frequencySort(string s) {        map<char,int> count;        for(int i=0;i<s.length();i++)            count[s[i]]++;        vector<pair<char,int>> sortCount;        for(map<char,int>::iterator it=count.begin();it!=count.end();it++)        {            pair<char,int> temp(it->first,it->second);            sortCount.push_back(temp);        }        sort(sortCount.begin(),sortCount.end(),cmp);        string result;        for(int i=0;i<sortCount.size();i++)            result.append(sortCount[i].second,sortCount[i].first);        return result;    }};