/// <summary>
/// checks whether removal of the cell is possible move
/// </summary>
/// <param name="cellToRemove"></param>
/// <returns>Was the removal successful?</returns>
private bool IsPossibleToRemoveValue(SudokuCell cellToRemove)
{
int row = Board.GetRow(cellToRemove);
int column = Board.GetColumn(cellToRemove);
int value = int.Parse(Board[row, column].Value);
if (!ValueCanBeElsewhere(cellToRemove) || CanCellContainAnotherValue(row, column, value))
{
return(true);
}
return(false);
}
/// <summary>
/// check if value of <paramref name="cellWithValue"/> can be elsewhere in the board
/// </summary>
/// <param name="cellWithValue"></param>
/// <returns></returns>
private bool ValueCanBeElsewhere(SudokuCell cellWithValue)
{
if (cellWithValue.IsEmpty())
{
throw new ArgumentException($"Argument is not valid: {nameof(cellWithValue)} is an empty cell");
}
int row = Board.GetRow(cellWithValue);
int column = Board.GetColumn(cellWithValue);
int value = int.Parse(Board[row, column].Value);
var emptyRowValues = Board.GetNthRow(row).GetEmptyCells();
var emptyColumnValues = Board.GetNthColumn(column).GetEmptyCells();
var emptySquareValues = Board.GetSquareFromPosition(row, column).GetAllCells().GetEmptyCells();
var allValues = new List <List <SudokuCell> >()
{
emptyRowValues, emptyColumnValues, emptySquareValues
};
// try to place value into other cells in the row, column and square
foreach (var selectedValues in allValues)
{
bool isOnlyPlaceForValue = true;
foreach (SudokuCell selectedCell in selectedValues)
{
cellWithValue.ClearValue();
selectedCell.Value = value.ToString();
var cellsRow = Board.GetNthRow(Board.GetRow(selectedCell));
var cellsCol = Board.GetNthColumn(Board.GetColumn(selectedCell));
var cellsSquare = Board.GetSquareFromPosition(Board.GetRow(selectedCell), Board.GetColumn(selectedCell)).GetAllCells();
if (cellsRow.IsSudokuValid() && cellsCol.IsSudokuValid() && cellsSquare.IsSudokuValid())
{
isOnlyPlaceForValue = false;
}
selectedCell.ClearValue();
cellWithValue.Value = value.ToString();
cellWithValue.IsDefaultValue = true;
}
if (isOnlyPlaceForValue)
{
return(false);
}
}
return(true);
}
public static bool IsValid(this Board board)
{
return(!board.Squares.Any(square => !square.IsValid()) &&
!Enumerable.Range(1, board.Size).Any(row => !board.GetRow(row).IsValid()) &&
!Enumerable.Range(1, board.Size).Any(column => !board.GetColumn(column).IsValid()));
}