Question

I am working on a program that reads a series of ints from a text file into a 2D array.

The file contains 40 lines of 81 numbers that have no spaces between them.

The problem is that when I cout the array after the loop has finished, it is outputting 2 random numbers in array[0][0] and array[0][1] before the expected output. I think it has to do with the newline/carriage return characters. The first iteration of the loop runs perfectly. Here is the code:

#include <cstring>
#include <cstdlib>
#include <iostream>
#include <fstream>

using namespace std;

int main()
{
  int array[9][9];

  //Open file:

  fstream ifile;

  ifile.open("numbers.txt", ios::in);
  if (ifile.fail())
    {
      cout << "Could not open numbers.txt" << endl;
      return -1;
    }

   while (!ifile.eof())
    {
      for(int i=0; i<9; i++)
      {   
    for(int j=0; j<9; j++)
    {
       int n = ifile.get();
              if(isdigit(n)) 
            {
                  array[i][j] = n - '0';
        }

          cout<<"array ["<<i<<"]["<<j<<"] is "<<array[i][j]<<endl;
      } 
      } cout<<"This is a test"<<endl;
    }

  return 0;
}

Answer 1

The random numbers appear because you increment j regardless of whether you write to grid[i][j].

Try replacing your inner loop with:

for(int j=0; j<9; )
{
  int n = file.get();
  if(!file) break;
  if(isdigit(n))
  {
    array[i][j] = n - '0';
    cout<<"array ["<<i<<"]["<<j<<"] is "<<array[i][j]<<endl;
    j++;
  }
  cout<<"grid ["<<i<<"]["<<j<<"] is "<<grid[i][j]<<endl;
}