一个文件程序，里面有点小问题

#include <fstream>
#include <iostream>
using namespace std;

int main()
{
  int a[10];
  cout << "Please input 10 interger: \n";
  for(int i=0; i<10; i++)
    {
      cin >> a[i];
    }
  
  ofstream outfile("exercise_4.txt", ios::out| ios::trunc);
  if(!outfile)
    {
      cerr << "Can't create file!\n";
      return 1;
    }

  for(int i=0; i<10; i++)
    {
      outfile << a[i] <<" ";
    }
  outfile.close();
  // this is the end of first part.
  
  ifstream infile("exercise_4.txt", ios::in);
  if(!infile)
    {
      cerr << "Can't open file!\n";
      return 1;
    }
  int b[10];
  for(int i=0; i<10; i++)
    {
      infile >> b[i];
    }
  infile.close();

  int max=b[0];
  int index = -1;
  for(int i=1; i<10; i++)
    if(b[i] > max)
      {
        max = b[i];
        index = i;
      }
  cout << "max= "<< max << endl;
  cout << "index= "<< index+1 << endl;
  cout << "This program ends." << endl;
  return 0;
}