private static Task <bool> IsValuePossibleAsync(byte[] boardData, int zeroBasedRowIndex, int zeroBasedColumnIndex, byte value)
{
Board.BoardDataContract(boardData);
Board.IndexValidContract(zeroBasedColumnIndex);
Board.IndexValidContract(zeroBasedRowIndex);
Board.CellValueContract(value);
// Note how we run the three tests in parallel. They are independent of each other.
var tasks = new Task <bool> [3];
tasks[0] = Task.Run <bool>(() => Board.IsValuePossibleInRow(boardData, zeroBasedRowIndex, value));
tasks[1] = Task.Run <bool>(() => Board.IsValuePossibleInColumn(boardData, zeroBasedColumnIndex, value));
tasks[2] = Task.Run <bool>(() => Board.IsValuePossibleInSquare(boardData, zeroBasedRowIndex, zeroBasedColumnIndex, value));
return(Task.Factory.ContinueWhenAll(tasks, t => t[0].Result && t[1].Result && t[2].Result));
}
/// <summary>
/// Internal implementation for setting a cell's value.
/// </summary>
private static bool TrySetCellInternal(byte[] boardData, int zeroBasedRowIndex, int zeroBasedColumnIndex, byte value)
{
Board.BoardDataContract(boardData);
Board.IndexValidContract(zeroBasedRowIndex);
Board.IndexValidContract(zeroBasedColumnIndex);
Board.CellValueContract(value, allowZero: false);
if (Board.IsValuePossible(boardData, zeroBasedRowIndex, zeroBasedColumnIndex, value))
{
boardData[Board.CalculateIndexFromRowAndColumn(zeroBasedRowIndex, zeroBasedColumnIndex)] = value;
return(true);
}
return(false);
}
private static bool IsValuePossibleInColumn(byte[] boardData, int zeroBasedColumnIndex, byte value)
{
Board.BoardDataContract(boardData);
Board.IndexValidContract(zeroBasedColumnIndex);
Board.CellValueContract(value);
for (int i = 0, index = zeroBasedColumnIndex; i < 9; i++, index += 9)
{
if (boardData[index] == value)
{
return(false);
}
}
return(true);
}
private static bool IsValuePossibleInSquare(byte[] boardData, int zeroBasedRowIndex, int zeroBasedColumnIndex, byte value)
{
Board.BoardDataContract(boardData);
Board.IndexValidContract(zeroBasedColumnIndex);
Board.IndexValidContract(zeroBasedRowIndex);
Board.CellValueContract(value);
for (int r = 0, rowIndex = (zeroBasedRowIndex / 3) * 3; r < 3; r++, rowIndex++)
{
for (int c = 0, columnIndex = (zeroBasedColumnIndex / 3) * 3; c < 3; c++, columnIndex++)
{
if (boardData[(rowIndex * 9) + columnIndex] == value)
{
return(false);
}
}
}
return(true);
}
