private SolvedSudokuGrid RecursivelySolve(SudokuGrid sudokuGrid, int row, int col)
{
var currentGrid = new SudokuGrid(sudokuGrid);
var gridValue = currentGrid.GetGridValue(row, col);
currentGrid.UpdateCandidateValues(row, col, gridValue.Value);
var coords = currentGrid.GetSmallestCandidateValuesCellCoordinates();
var values = currentGrid.GetCandidateValues(coords.Item1, coords.Item2);
if (values.Count == 0)
{
if (IsSolved(currentGrid))
{
return(new SolvedSudokuGrid(currentGrid, true, true));
}
return(new SolvedSudokuGrid(currentGrid, true, false));
}
SolvedSudokuGrid previouslySolvedGrid = null;
foreach (var value in values.ToList())
{
currentGrid.SetGridValue(coords.Item1, coords.Item2, value);
var solvedGrid = RecursivelySolve(currentGrid, coords.Item1, coords.Item2);
if (solvedGrid.Solvable && (solvedGrid.Unique == false || previouslySolvedGrid != null))
{
return(new SolvedSudokuGrid(solvedGrid.SolvedGrid, false, true));
}
if (solvedGrid.Solvable && previouslySolvedGrid == null)
{
previouslySolvedGrid = new SolvedSudokuGrid(solvedGrid.SolvedGrid, true, true);
}
}
if (previouslySolvedGrid != null)
{
return(new SolvedSudokuGrid(previouslySolvedGrid.SolvedGrid, previouslySolvedGrid.Unique, true));
}
return(new SolvedSudokuGrid(currentGrid, true, false));
}
public SudokuGrid GenerateGrid(GameType gameType)
{
var grid = new SudokuGrid();
bool unique;
var count = 0;
while (true)
{
while (count < 22)
{
var row = new Random().Next(0, 9);
var column = new Random().Next(0, 9);
var value = new Random().Next(1, 10);
if (grid.GetGridValue(row, column).Value == 0)
{
if (SudokuSolver.IsValidMove(row, column, value, grid))
{
grid.SetGridValue(row, column, value, true);
count++;
}
}
}
var solvedGrid = SudokuSolver.Solve(new SudokuGrid(grid));
if (solvedGrid.Solvable)
{
unique = solvedGrid.Unique;
break;
}
grid = new SudokuGrid();
count = 0;
}
while (unique == false)
{
var row = new Random().Next(0, 9);
var column = new Random().Next(0, 9);
var value = new Random().Next(1, 10);
if (grid.GetGridValue(row, column).Value == 0)
{
if (SudokuSolver.IsValidMove(row, column, value, grid))
{
grid.SetGridValue(row, column, value, true);
var solvedGrid = SudokuSolver.Solve(new SudokuGrid(grid));
if (solvedGrid.Solvable == false)
{
grid.SetGridValue(row, column, 0, false);
}
else
{
unique = solvedGrid.Unique;
}
}
}
}
return(grid);
}
