/// <summary>
/// Generate sudoku to fill from full-filled sudoku
/// </summary>
/// <param name="sudoku"></param>
/// <param name="notCheckedPositionsFromPrev"></param>
/// <param name="difficultyPoints"></param>
/// <param name="symmetry"></param>
/// <param name="token">Cancellation token</param>
/// <returns></returns>
private static bool GenerateFromFull(Domain.Sudoku sudoku, IEnumerable <Tuple <int, int> > notCheckedPositionsFromPrev,
int difficultyPoints, Enums.SymmetryType symmetry, CancellationToken token)
{
var notCheckedPositions = new List <Tuple <int, int> >(notCheckedPositionsFromPrev);
while (notCheckedPositions.Count > 0)
{
token.ThrowIfCancellationRequested();
var removedCells = RemoveNext(sudoku, notCheckedPositions, symmetry);
var solutions = Solver.GetTopNSolutions(sudoku, 2, Enums.TopType.Any);
if (solutions.Count == 1 && solutions.First().DifficultyPoints > difficultyPoints)
{
sudoku.DifficultyPoints = solutions.First().DifficultyPoints;
return(true);
}
if (solutions.Count > 1)
{
RecoverCells(sudoku, removedCells);
return(false);
}
if (GenerateFromFull(sudoku, notCheckedPositions, difficultyPoints, symmetry, token))
{
return(true);
}
RecoverCells(sudoku, removedCells);
}
return(false);
}
private static List <Cell> RemoveNext(Domain.Sudoku sudoku, IList <Tuple <int, int> > notCheckedPositions, Enums.SymmetryType symmetry)
{
var randomPosition = Random.Next(0, notCheckedPositions.Count - 1);
var currentCell = notCheckedPositions[randomPosition];
notCheckedPositions.RemoveAt(randomPosition);
var row = currentCell.Item1;
var column = currentCell.Item2;
var removedValues = new List <Cell>()
{
new Cell(row, column, sudoku[row, column])
};
sudoku[row, column] = 0;
if (symmetry == Enums.SymmetryType.Horizontal)
{
if (row == 4)
{
return(removedValues);
}
var symmetricRow = Domain.Sudoku.BigSide - 1 - row;
removedValues.Add(new Cell(symmetricRow, column, sudoku[symmetricRow, column]));
notCheckedPositions.Remove(Tuple.Create(symmetricRow, column));
sudoku[symmetricRow, column] = 0;
}
else if (symmetry == Enums.SymmetryType.Vertical)
{
if (column == 4)
{
return(removedValues);
}
var symmetricColumn = Domain.Sudoku.BigSide - 1 - column;
removedValues.Add(new Cell(row, symmetricColumn, sudoku[row, symmetricColumn]));
notCheckedPositions.Remove(Tuple.Create(row, symmetricColumn));
sudoku[row, symmetricColumn] = 0;
}
return(removedValues);
}