项目3（文件流）

#include <iostream>
#include <Windows.h>
#include <fstream>
using namespace std;
int main(void)
{
  ifstream stream;
  int max, min, sum = 0;
  int num;
  int n = 0;
  stream.open("num.txt");
  if (!stream.is_open())
  {
    cout << "文件打开失败" << endl;
    exit(1);
  }
  stream >> num;
  n++;
  max = num;
  min = num;
  sum = sum + num;
  while (!stream.eof())
  {
    stream >> num;
    stream >> num;
    if (num > max)
    {
      max = num;
    }
    if (num < min)
    {
      min = num;
    }
    sum = sum + num;
    n++;
  }
  cout << "平均值：" << num / n << endl;
  cout << "和：" << sum << endl;
  cout << "最大值：" << max << endl;
  cout << "最小值：" << min << endl;
  system("pause");
  return 0;
}