private void SolveByBruteForce(SudokuBoard board)
{
var listOfAttempts = new List <Attempt>();
foreach (var sudokuRow in board.Rows)
{
foreach (var sudokuRowCell in sudokuRow.Cells.Where(c => !c.IsFilled))
{
var column = board.Columns.FirstOrDefault(c => c.ColumnNumber == sudokuRowCell.ColumnNumber);
var squareNumber = SudokuBoard.CalculateSquareNumber(sudokuRowCell.RowNumber, sudokuRowCell.ColumnNumber);
var square = board.Squares.FirstOrDefault(s => s.SquareNumber == squareNumber);
var unusedNumber = 0;
for (int i = 1; i <= board.NumbersPerUnit; i++)
{
if (!sudokuRow.HasNumberBeenUsed(i) && !column.HasNumberBeenUsed(i) && !square.HasNumberBeenUsed(i) && !DoesAttemptExist(sudokuRowCell, i, listOfAttempts))
{
unusedNumber = i;
}
}
if (unusedNumber == 0)
{
continue;
}
//Try setting the number of the cell to the first unused number
listOfAttempts.Add(new Attempt(sudokuRowCell, unusedNumber));
var attemptBoard = board.Clone();
var attemptCell = attemptBoard.GetCell(sudokuRowCell.ColumnNumber, sudokuRowCell.RowNumber);
attemptCell.Number = unusedNumber;
SolveBoard(attemptBoard);
if (attemptBoard.IsSolved)
{
sudokuRowCell.Number = unusedNumber;
SolveBoard(board);
return;
}
}
}
}