c++统计输入中不同单词所出现的次数（续）

#include <map>
#include <vector>
#include <iostream>
#include <string>

using std::string;
using std::map;
using std::vector;
using std::cin;
using std::cout;
using std::endl;

int _tmain(int argc, _TCHAR* argv[])
{
	string word;
	map<string,int> counters;
	map<int,vector<string> > group_counters;  //将单词按出现次数分组

	cout<<"Please input words(Ctrl+z to end):"<<endl;
	while (cin>>word)
		++counters[word];

	for (map<string,int>::const_iterator iter = counters.begin();iter != counters.end();iter++)
		group_counters[iter->second].push_back(iter->first);

	for (map<int,vector<string> >::const_iterator iter = group_counters.begin();iter != group_counters.end();iter ++) {
		for (vector<string>::const_iterator it = iter->second.begin();it != iter->second.end();it++)
			cout<<*it<<"\t"<<iter->first<<endl;
	}
		
	return 0;
}