计算文件中所有单词出现的次数

给出一个文本文件，要求计算其中单词出现的次数，这里用到map容器求解。

文本文件信息如下：

From the hell to the heaven,
There's no straight way to walk.
Sometimes up, sometimes down.
Hope creates a heaven for us,
Despair makes a hell for us.

代码如下：

//计算文件中单词出现的次数，并按字典序输出
#include <iostream>
#include <fstream>
#include <map>
#include <string>
using namespace std;

int main()
{
	map<string,int> word_count;
	string word;

	//read content in ifile.txt into ifstream object "ifile".
	ifstream ifile("ifile.txt");
	//open file failed.
	if (!ifile)
	{
		cerr << "cannot open file!";
		exit(-1);
	}

	//pass a string object to word every once.
	while (ifile >> word)
		//add 1 to value, which responding to key "word".
		++word_count[word];
	
	map<string,int>::iterator iter;
	//output elements in map object "word_count".
	for(iter = word_count.begin();iter != word_count.end();++iter)
		cout << iter->first << ", " << iter->second << endl;

	return 0;
}

运行结果：