private void CreatePuzzleGrid(SudokuPuzzle puzzle, int maxBlanks)
{
var puzzleGrid = CopyGrid(puzzle.puzzleGrid);
int numBlanks = maxBlanks;
bool found = false;
//
// Start with number of blanks as specified in policy
// If multiple solutions are found, decrease the number of blank
// cells until a single solution is found
while (!found && numBlanks > 0)
{
int numRetries = 10;
int retries = 0;
while (retries < numRetries && !found)
{
var rng = new Random(Guid.NewGuid().GetHashCode());
var backupGrid = CopyGrid(puzzleGrid);
int numRemainingBlanks = numBlanks;
while (numRemainingBlanks > 0)
{
int row = rng.Next(9);
int col = rng.Next(9);
while (puzzleGrid[row, col] == 0)
{
row = rng.Next(9);
col = rng.Next(9);
}
puzzleGrid[row, col] = 0;
numRemainingBlanks--;
}
var copy = CopyGrid(puzzleGrid);
puzzle.NumSolutions = _solver.SolveGrid(copy);
if (puzzle.NumSolutions > 1)
{
Console.WriteLine($"Too many solutions: {puzzle.NumSolutions}");
}
else if (puzzle.NumSolutions == 0)
{
Console.WriteLine("No solution found");
}
if (puzzle.NumSolutions != 1)
{
puzzleGrid = backupGrid;
}
else
{
found = true;
}
retries++;
}
numBlanks--;
}
puzzle.puzzleGrid = CopyGrid(puzzleGrid);
}