STL

// SP-STL-02.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <iterator>
#include <map>

using namespace std;

map<int,unsigned int> statistic_map;
map<int,unsigned int>::iterator m_iter;
int _tmain(int argc, _TCHAR* argv[])
{
    ifstream file("a.txt");
    istream_iterator<int> i(file);
    while (i!=istream_iterator<int>())
    {
        int key=*i++;
        m_iter=statistic_map.find(key);
        if (m_iter==statistic_map.end())
        {
            statistic_map.insert(make_pair(key,1));
        }
        else
        {
            unsigned int n=statistic_map[key];
            statistic_map[key]=n+1;
        }
    }

    for (m_iter=statistic_map.begin();
        m_iter!=statistic_map.end(); m_iter++)
    {
        cout << m_iter->first << " " << m_iter->second<< endl;
    }
    return 0;
}