private bool _FillMissingNumbers(int[,] board)
{
UnfilledPosition position = new UnfilledPosition(-1, -1);
position = _GetMissingPosition(board);
//If there is no missing number, the problem is solved!
if (!IndeedMissing(position))
{
return(true);
}
for (int numberToBeFilled = 1; numberToBeFilled < 10; numberToBeFilled++)
{
if (CanThisNumberFilled(board, position.GetRowPosition(),
position.GetColumnPosition(), numberToBeFilled))
{
board[position.GetRowPosition(), position.GetColumnPosition()] = numberToBeFilled;
//Recurse for other missing numbers
if (_FillMissingNumbers(board))
{
return(true);
}
else
{
//Backtrack -> Reset the filled number
board[position.GetRowPosition(), position.GetColumnPosition()] = 0;
}
}
}
return(false);
}
private UnfilledPosition _GetMissingPosition(int[,] board)
{
UnfilledPosition unfilledPosition = new UnfilledPosition(-1, -1);
for (int index = 0; index < 9; index++)
{
for (int secIndex = 0; secIndex < 9; secIndex++)
{
if (board[index, secIndex] == 0)
{
unfilledPosition.SetRowPosition(index);
unfilledPosition.SetColumnPosition(secIndex);
break;
}
}
//Break out of outer for if missing position is found
if (IndeedMissing(unfilledPosition))
{
break;
}
}
return(unfilledPosition);
}
private bool IndeedMissing(UnfilledPosition unfilledPosition)
{
return(unfilledPosition.GetRowPosition() != -1 &&
unfilledPosition.GetColumnPosition() != -1);
}