/// <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);
}
/// <summary>
/// Check if Sudoku remain consistent if we put number in specified location
/// </summary>
/// <param name="board">Board to check</param>
/// <param name="row">row in board</param>
/// <param name="column">column in board</param>
/// <param name="value">value to put</param>
/// <returns></returns>
public static bool ConsistentIfPut(Domain.Sudoku board, int row, int column, int value)
{
for (var i = 0; i < Domain.Sudoku.BigSide; i++)
{
if (board[row, i] == value)
{
return(false);
}
if (board[i, column] == value)
{
return(false);
}
}
var rowStart = row - row % Domain.Sudoku.SmallSide;
var columnStart = column - column % Domain.Sudoku.SmallSide;
for (var m = 0; m < Domain.Sudoku.SmallSide; m++)
{
for (var k = 0; k < Domain.Sudoku.SmallSide; k++)
{
if (board[rowStart + k, columnStart + m] == value)
{
return(false);
}
}
}
return(true);
}
private void ClearAndSolve(Domain.Sudoku sudoku, int currentIndex, Enums.TopType type, int count)
{
_currentIterationsCount = 0;
_solutions.Clear();
SolveBruteForce(sudoku, currentIndex, type, count);
}
private static void RecoverCells(Domain.Sudoku sudoku, IList <Cell> cellsToRecover)
{
foreach (var cell in cellsToRecover)
{
sudoku[cell.Row, cell.Column] = cell.Value;
}
cellsToRecover.Clear();
}
/// <summary>
/// Count number of solutions for given sudoku
/// </summary>
/// <param name="sudoku"></param>
/// <returns></returns>
public int CountSolutions(Domain.Sudoku sudoku)
{
if (sudoku == null)
{
throw new ArgumentNullException(nameof(sudoku));
}
ClearAndSolve(sudoku.Copy(), 0, Enums.TopType.Any, int.MaxValue);
return(_solutions.Count);
}
/// <summary>
/// Solve sudoku and return first available solution
/// </summary>
/// <param name="sudoku"></param>
/// <returns></returns>
public Domain.Sudoku SolveSudoku(Domain.Sudoku sudoku)
{
if (sudoku == null)
{
throw new ArgumentNullException(nameof(sudoku));
}
ClearAndSolve(sudoku.Copy(), 0, Enums.TopType.Any, 1);
return(_solutions.FirstOrDefault());
}
/// <summary>
/// Save sudoku to local file named <see cref="LocalFile"/>
/// </summary>
/// <param name="sudoku"><see cref="Domain.Sudoku"/>></param>
/// <returns></returns>
public static async Task SaveSudokuAsync(Domain.Sudoku sudoku)
{
if (sudoku == null)
{
throw new NullReferenceException(nameof(sudoku));
}
using (var fileStream = new FileStream(LocalFile, FileMode.Create))
using (var stream = new StreamWriter(fileStream))
{
await stream.WriteAsync(sudoku.ToString());
}
}
internal static Domain.Sudoku GenerateFull()
{
var sudoku = new Domain.Sudoku();
for (var i = 0; i < Domain.Sudoku.BigSide; i++)
{
for (var j = 0; j < Domain.Sudoku.BigSide; j++)
{
sudoku[i, j] = (i * Domain.Sudoku.SmallSide + i / Domain.Sudoku.SmallSide + j) % Domain.Sudoku.BigSide + 1;
}
}
return(sudoku);
}
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);
}
/// <summary>
/// Solve sudoku and return given number of solutions in given order
/// </summary>
/// <param name="sudoku"> Sudoku to solve </param>
/// <param name="count"> Number of solutions to return </param>
/// <param name="topType"> Sort order </param>
/// <returns></returns>
public List <Domain.Sudoku> GetTopNSolutions(Domain.Sudoku sudoku, int count, Enums.TopType topType)
{
if (sudoku == null)
{
throw new ArgumentNullException(nameof(sudoku));
}
if (count < 0)
{
throw new Exception("Number of solutions can not be negative value");
}
ClearAndSolve(sudoku.Copy(), 0, topType, count);
return(topType == Enums.TopType.Hardest
? _solutions.Skip(Math.Max(0, _solutions.Count - count)).ToList()
: _solutions.ToList());
}
private static bool CheckSudoku(Domain.Sudoku sudoku)
{
var vHash = new HashSet <int>();
var hHash = new HashSet <int>();
for (var i = 0; i < 9; i++)
{
for (var j = 0; j < 9; j++)
{
vHash.Clear();
hHash.Clear();
for (var k = 0; k < Domain.Sudoku.BigSide; k++)
{
if (vHash.Contains(sudoku[i, k]))
{
return(false);
}
vHash.Add(sudoku[i, k]);
if (hHash.Contains(sudoku[k, j]))
{
return(false);
}
hHash.Add(sudoku[k, j]);
}
var rowStart = i - i % Domain.Sudoku.SmallSide;
var columnStart = j - j % Domain.Sudoku.SmallSide;
vHash.Clear();
for (var m = 0; m < Domain.Sudoku.SmallSide; m++)
{
for (var k = 0; k < Domain.Sudoku.SmallSide; k++)
{
if (vHash.Contains(sudoku[rowStart + k, columnStart + m]))
{
return(false);
}
vHash.Add(sudoku[rowStart + k, columnStart + m]);
}
}
}
}
return(true);
}
private static bool ValidateSubSquare(Domain.Sudoku board, int colStart, int rowStart)
{
var set = new bool[Domain.Sudoku.BigSide + 1];
for (var i = 0; i < Domain.Sudoku.SmallSide; i++)
{
for (var j = 0; j < Domain.Sudoku.SmallSide; j++)
{
if (board[rowStart + i, colStart + j] != 0 && set[board[rowStart + i, colStart + j]])
{
return(false);
}
set[board[rowStart + i, colStart + j]] = true;
}
}
return(true);
}
private bool SolveBruteForce(Domain.Sudoku sudoku, int currentIndex, Enums.TopType type, int count)
{
while (true)
{
if (currentIndex == Domain.Sudoku.BigSide * Domain.Sudoku.BigSide)
{
var solutionBoard = sudoku.Copy();
solutionBoard.DifficultyPoints = _currentIterationsCount;
_solutions.Add(solutionBoard);
return(true);
}
else
{
var row = currentIndex / Domain.Sudoku.BigSide;
var column = currentIndex % Domain.Sudoku.BigSide;
if (sudoku[row, column] != 0)
{
currentIndex = currentIndex + 1;
continue;
}
for (var i = 1; i <= Domain.Sudoku.BigSide; i++)
{
_currentIterationsCount++;
if (!Validations.ConsistentIfPut(sudoku, row, column, i))
{
continue;
}
sudoku[row, column] = i;
if (SolveBruteForce(sudoku, currentIndex + 1, type, count) &&
(type == Enums.TopType.Any || type == Enums.TopType.Easiest) && _solutions.Count >= count)
{
return(true);
}
sudoku[row, column] = 0;
}
}
return(false);
}
}
internal static void RunShuffle(Domain.Sudoku sudoku, int shufflesCount, CancellationToken token)
{
for (var i = 0; i < shufflesCount; i++)
{
token.ThrowIfCancellationRequested();
var firstParam = Random.Next(0, 2);
var secondParam = Random.Next(0, 2);
var thirdParam = Random.Next(0, 2);
// to avoid exchange between one row/column
while (secondParam == thirdParam)
{
thirdParam = Random.Next(0, 2);
}
var shuffleMethod = Random.Next(0, 4);
switch (shuffleMethod)
{
case 0:
sudoku.Transpose();
break;
case 1:
sudoku.SwapSmallRows(firstParam, secondParam, thirdParam);
break;
case 2:
sudoku.SwapSmallColumns(firstParam, secondParam, thirdParam);
break;
case 3:
sudoku.SwapBigRows(secondParam, thirdParam);
break;
case 4:
sudoku.SwapBigColumns(secondParam, thirdParam);
break;
}
}
}
/// <summary>
/// Import Sudoku from file
/// </summary>
/// <param name="path">Path to .txt file</param>
/// <returns><see cref="Domain.Sudoku"/></returns>
public static async Task <Domain.Sudoku> ReadFromFileAsync(string path)
{
if (!File.Exists(path))
{
return(null);
}
var fileInfo = new FileInfo(path);
var sudoku = new Domain.Sudoku();
var lineNumber = 0;
using (var stream = new StreamReader(fileInfo.OpenRead()))
{
while (stream.Peek() >= 0)
{
var line = await stream.ReadLineAsync();
if (line.Length != Domain.Sudoku.BigSide)
{
throw new Exception($"Incorrect sudoku. Line {lineNumber} has length of {line.Length}");
}
for (var column = 0; column < line.Length; column++)
{
if (int.TryParse(line[column].ToString(), out var num) && num != 0)
{
sudoku[lineNumber, column] = num;
}
else
{
sudoku[lineNumber, column] = 0;
}
}
lineNumber++;
}
}
return(sudoku);
}
private static bool ValidateRowColumn(Domain.Sudoku board, int idx)
{
var rowSet = new bool[Domain.Sudoku.BigSide + 1];
var colSet = new bool[Domain.Sudoku.BigSide + 1];
for (var i = 0; i < Domain.Sudoku.BigSide; i++)
{
if (board[idx, i] != 0 && rowSet[board[idx, i]])
{
return(false);
}
if (board[i, idx] != 0 && colSet[board[i, idx]])
{
return(false);
}
rowSet[board[idx, i]] = true;
colSet[board[i, idx]] = true;
}
return(true);
}
/// <summary>
/// Validate sudoku if it's consistent
/// </summary>
/// <param name="board"></param>
/// <returns></returns>
public static bool ValidateSudoku(Domain.Sudoku board)
{
for (var i = 0; i < Domain.Sudoku.BigSide; i++)
{
if (!ValidateRowColumn(board, i))
{
return(false);
}
}
for (var i = 0; i < Domain.Sudoku.BigSide; i += Domain.Sudoku.SmallSide)
{
for (var j = 0; j < Domain.Sudoku.BigSide; j += Domain.Sudoku.SmallSide)
{
if (!ValidateSubSquare(board, i, j))
{
return(false);
}
}
}
return(true);
}