public bool TryAndSolveOnce(SudokuGrid inputGrid)
{
while (inputGrid.FindAllEmptySquares().Count != 0)
{
bool hasASquareBeenFilled = false;
foreach (var emptySquare in inputGrid.FindAllEmptySquares())
{
List <int> validOptionsForSquare = DetermineValidOptionsForSquare(emptySquare, inputGrid);
if (validOptionsForSquare.Count == 0)
{
return(false);
}
if (validOptionsForSquare.Count == 1)
{
inputGrid.FillInSquare(emptySquare, validOptionsForSquare[0]);
hasASquareBeenFilled = true;
}
}
if (!hasASquareBeenFilled)
{
return(true);
}
}
return(true);
}
public bool TryAndSolveOnce(SudokuGrid inputGrid)
{
while (inputGrid.FindAllEmptySquares().Count != 0)
{
bool hasASquareBeenFilled = false;
foreach (var emptySquare in inputGrid.FindAllEmptySquares())
{
List<int> validOptionsForSquare = DetermineValidOptionsForSquare(emptySquare, inputGrid);
if (validOptionsForSquare.Count == 0)
{
return false;
}
if (validOptionsForSquare.Count == 1)
{
inputGrid.FillInSquare(emptySquare, validOptionsForSquare[0]);
hasASquareBeenFilled = true;
}
}
if (!hasASquareBeenFilled)
{
return true;
}
}
return true;
}
public SudokuGrid Solve(SudokuGrid inputGrid)
{
bool returnFromOneSolve = TryAndSolveOnce(inputGrid);
if (!returnFromOneSolve)
{
return(null);
}
if (inputGrid.FindAllEmptySquares().Count != 0)
{
Console.WriteLine("Solving failed at this step");
}
return(inputGrid);
}
public SudokuGrid Solve(SudokuGrid inputGrid)
{
bool returnFromOneSolve = TryAndSolveOnce(inputGrid);
if (!returnFromOneSolve)
{
return null;
}
if (inputGrid.FindAllEmptySquares().Count != 0)
{
Console.WriteLine("Solving failed at this step");
}
return inputGrid;
}
private ImmutableSudokuGrid Solve(ImmutableSudokuGrid grid, SudokuSolver simpleSolver, bool isRandomSolve, int disallowedValue, int disallowedRow, int disallowedColumn)
{
SudokuGrid mutableGrid = grid.MakeMutableCopy();
bool isGridValid = simpleSolver.TryAndSolveOnce(mutableGrid);
grid = new ImmutableSudokuGrid(mutableGrid.Elements);
if (!isGridValid)
{
return(null);
}
var emptySquareList = grid.FindAllEmptySquares();
if (emptySquareList.Count == 0)
{
return(grid);
}
SquareCoordinate emptySquareToFill = emptySquareList[0];
if (isRandomSolve)
{
var randomEmptySquare = new Random().Next(emptySquareList.Count - 1);
emptySquareToFill = emptySquareList[randomEmptySquare];
}
var validOptions = simpleSolver.DetermineValidOptionsForSquare(emptySquareToFill, grid);
if (emptySquareToFill.Row == disallowedRow && emptySquareToFill.Column == disallowedColumn && disallowedValue != 0)
{
validOptions.Remove(disallowedValue);
}
for (int i = 0; i < validOptions.Count; i++)
{
ImmutableSudokuGrid solvedGrid = Solve(grid.WithExtraSquare(emptySquareToFill, validOptions[i]), isRandomSolve);
if (solvedGrid != null)
{
return(solvedGrid);
}
}
return(null);
}