C++实现按照map的value排序

//功能：输入单词，统计单词出现次数并按照单词出现次数从多到少排序  
#include <iostream>
#include <cstdlib>  
#include <map>  
#include <vector>  
#include <string>  
#include <algorithm>  

using namespace std;
   
int cmp(const pair<string, int>& x, const pair<string, int>& y)  
{  
    return x.second > y.second;  
}  
   
void sortMapByValue(map<string, int>& tMap,vector<pair<string, int> >& tVector)  
{  
    for (map<string, int>::iterator curr = tMap.begin(); curr != tMap.end(); curr++)   
        tVector.push_back(make_pair(curr->first, curr->second));    
   
    sort(tVector.begin(), tVector.end(), cmp);  
}  
int main()  
{  
    map<string, int> tMap;  
    string word;  
    while (cin >> word)  
    {  
        pair<map<string,int>::iterator,bool> ret = tMap.insert(make_pair(word, 1));  
        if (!ret.second)  
            ++ret.first->second;  
    }   
   
    vector<pair<string,int>> tVector;  
    sortMapByValue(tMap,tVector);  
    for(int i=0;i<tVector.size();i++)  
        cout<<tVector[i].first<<": "<<tVector[i].second<<endl;  
   
    system("pause");  
    return 0;  
}