C++从一个文件中统计所有出现过的单词,并按次数从大到小输出

#include <iostream>#include <string>#include <fstream>#include <map>#include <algorithm>using namespace std;int main(){ifstream input;input.open("word.txt");string eachline;map<string, int> mapA; //第一个存单词,第二个存单词出现的次数;while (getline(input, eachline)){string::size_type start = 0;string::size_type end = eachline.find_first_of(" ");while (end != string::npos) //npos就是这一行到头啦；{string content = eachline.substr(start, end - start);map<string, int>::iterator it = mapA.find(content);if (it == mapA.end()){mapA.insert(pair<string, int>(content, 1));//赋值的时候只接受pair类型；} else{++it->second;}start = end + 1;end = eachline.find_first_of(" ", start);}}multimap<int, string, greater<int> > mapB;for (map<string, int>::iterator it1 = mapA.begin(); it1 != mapA.end();++it1){mapB.insert(pair<int, string>(it1->second, it1->first));}for (map<int, string>::iterator it2 = mapB.begin(); it2 != mapB.end();++it2){//if ((it2->first) > 1)cout << it2->second << "单词出现的次数是" << it2->first << endl;}}