private bool IsSolvable(SudokuBoard board, Position position)
{
var availableNumbers = board.GetAllAvailableNumbersForCell(position);
_isSolved = !board.ContainsZero() && IsFinalPosition(position);
var nextAvailablePosition = Position.GetNextAvailablePosition(position);
for (var num = 0; num < availableNumbers.Count; num++)
{
if (_isSolved)
{
break;
}
var number = availableNumbers[num];
if (IsNotValidNumber(board, position, nextAvailablePosition, number))
{
continue;
}
board.Set(position, number);
IsSolvable(board, nextAvailablePosition);
SetCurrentPositionToZero(board, position);
}
return(_isSolved);
}
private static bool NextCellCanHoldOnlyCurrentNumber(SudokuBoard board, Position nextAvailablePosition, int num)
{
return(board.GetAllAvailableNumbersForCell(nextAvailablePosition).Count == 1 &&
board.GetAllAvailableNumbersForCell(nextAvailablePosition)[0] == num);
}