Sample Run

Enter name of file containing board:
correct.txt
1 [ 8 | 6 | 1 || 7 | 2 | 9 || 4 | 5 | 3 ]
2 [ 4 | 9 |   || 3 | 6 | 5 || 1 | 7 | 8 ]
3 [ 5 | 7 | 3 || 1 | 4 | 8 || 6 | 2 | 9 ]
   -----------  -----------  -----------
4 [ 1 | 4 | 9 || 5 | 8 | 3 || 2 | 6 | 7 ]
5 [ 2 | 3 | 7 || 9 | 1 | 6 || 8 | 4 | 5 ]
6 [ 6 | 5 | 8 || 2 | 7 | 4 || 3 | 9 | 1 ]
   -----------  -----------  -----------
7 [ 3 | 1 | 5 || 6 | 9 | 2 || 7 | 8 | 4 ]
8 [ 9 | 2 | 4 || 8 | 3 | 7 || 5 | 1 | 6 ]
9 [ 7 | 8 | 6 || 4 | 5 | 1 || 9 | 3 |   ]
   -----------  -----------  -----------
  =======================================
  | 1 | 2 | 3 || 4 | 5 | 6 || 7 | 8 | 9 |
Time to make a guess!
Enter row:
1
Enter column:
1
Enter value:
43
Invalid selection.  Enter value (again):
2
You cannot change the value in that position!
Try again.
Enter row:
2
Enter column:
34
Invalid selection.  Enter column (again):
54
Invalid selection.  Enter column (again):
3
Enter value:
2
1 [ 8 | 6 | 1 || 7 | 2 | 9 || 4 | 5 | 3 ]
2 [ 4 | 9 | 2 || 3 | 6 | 5 || 1 | 7 | 8 ]
3 [ 5 | 7 | 3 || 1 | 4 | 8 || 6 | 2 | 9 ]
   -----------  -----------  -----------
4 [ 1 | 4 | 9 || 5 | 8 | 3 || 2 | 6 | 7 ]
5 [ 2 | 3 | 7 || 9 | 1 | 6 || 8 | 4 | 5 ]
6 [ 6 | 5 | 8 || 2 | 7 | 4 || 3 | 9 | 1 ]
   -----------  -----------  -----------
7 [ 3 | 1 | 5 || 6 | 9 | 2 || 7 | 8 | 4 ]
8 [ 9 | 2 | 4 || 8 | 3 | 7 || 5 | 1 | 6 ]
9 [ 7 | 8 | 6 || 4 | 5 | 1 || 9 | 3 |   ]
   -----------  -----------  -----------
  =======================================
  | 1 | 2 | 3 || 4 | 5 | 6 || 7 | 8 | 9 |
Time to make a guess!
Enter row:
9
Enter column:
9
Enter value:
34
Invalid selection.  Enter value (again):
2
Congrats! You win!