private ImmutableSudokuGrid EmptyGridForSimpleSolve(ImmutableSudokuGrid inputGrid, SudokuSolver solver)
{
ImmutableSudokuGrid grid = inputGrid;
while (true)
{
bool hasSquareBeenRemoved = false;
List<SquareCoordinate> filledSquareList = grid.FindAllFilledSquares();
foreach (SquareCoordinate square in filledSquareList)
{
ImmutableSudokuGrid gridWithoutSquare = grid.WithoutSquare(square);
int numberOfOptions = solver.DetermineValidOptionsForSquare(square, gridWithoutSquare).Count;
if (numberOfOptions == 1)
{
grid = gridWithoutSquare;
hasSquareBeenRemoved = true;
}
}
if (!hasSquareBeenRemoved)
{
return grid;
}
}
}
private ImmutableSudokuGrid EmptyGridForSimpleSolve(ImmutableSudokuGrid inputGrid, SudokuSolver solver)
{
ImmutableSudokuGrid grid = inputGrid;
while (true)
{
bool hasSquareBeenRemoved = false;
List <SquareCoordinate> filledSquareList = grid.FindAllFilledSquares();
foreach (SquareCoordinate square in filledSquareList)
{
ImmutableSudokuGrid gridWithoutSquare = grid.WithoutSquare(square);
int numberOfOptions = solver.DetermineValidOptionsForSquare(square, gridWithoutSquare).Count;
if (numberOfOptions == 1)
{
grid = gridWithoutSquare;
hasSquareBeenRemoved = true;
}
}
if (!hasSquareBeenRemoved)
{
return(grid);
}
}
}
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);
}
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;
}
