/// <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);
}
/// <summary>
/// check if cell can have another value than <paramref name="value"/>
/// </summary>
/// <param name="row"></param>
/// <param name="column"></param>
/// <param name="value"></param>
/// <returns></returns>
private bool CanCellContainAnotherValue(int row, int column, int value)
{
// check if here can be another value, if no -> remove the value
var cellsRow = Board.GetNthRow(row).GetValuesFromCells();
var cellsCol = Board.GetNthColumn(column).GetValuesFromCells();
var cellsSquare = Board.GetSquareFromPosition(row, column).GetAllCells().GetValuesFromCells();
var invalidValues = cellsRow.Union(cellsCol).Union(cellsSquare).ToList();
invalidValues.Remove(value);
var validValues = this.Board.AllSudokuValues.Except(invalidValues);
if (validValues.Count() == 1 && validValues.First() == value)
{
return(true);
}
else
{
return(false);
}
}