private static void FindCandidatesPairsInCells(SolvingContext context, ICellGroup cellGroup)
{
var allNumbers = GetAllSudokuNumbers();
var unassignedValues = allNumbers.Except(cellGroup.Select(x => x.Value)).ToList();
var allNumbersCombinations = unassignedValues
.SelectMany(x => unassignedValues, Tuple.Create)
.Where(tuple => tuple.Item1 != tuple.Item2)
.ToList();
foreach (var combination in allNumbersCombinations)
{
var first = combination.Item1;
var firstValueCells = cellGroup.Where(x => x.CanPutCandidate(first)).ToList();
var second = combination.Item2;
var secondValueCells = cellGroup.Where(x => x.CanPutCandidate(second)).ToList();
if (firstValueCells.Count != 2 || secondValueCells.Count != 2 ||
!firstValueCells.SequenceEqual(secondValueCells))
{
continue;
}
foreach (var cell in firstValueCells)
{
context.CellsAffectedWithCrossOut += cell.RemoveCandidatesExcept(combination.ToArray());
}
RemoveCandidates(context, cellGroup, Tuple.Create(firstValueCells.First(), firstValueCells.Last()));
}
}
private static void SearchForSingleInGroup(SolvingContext context, ICellGroup group)
{
var allNumbers = Enumerable.Range(1, 9)
.Select(x => (short)x)
.Except(group.Select(x => x.Value).Distinct())
.ToList();
var singles = allNumbers.Select(x => new
{
Value = x,
ElligibleCellsCount = group.Count(y => y.CanPutCandidate(x))
})
.Where(x => x.ElligibleCellsCount == 1)
.Select(x => x.Value)
.ToList();
var single = singles.FirstOrDefault();
if (single == 0)
{
return;
}
var targetCell = group.FirstOrDefault(x => x.CanPutCandidate(single));
if (targetCell == null)
{
return;
}
var newCell = new Cell(single, targetCell.X, targetCell.Y);
context.Grid = context.Grid.UpdateCell(newCell);
context.FilledInCellsCount++;
context.GoToLoopStart = true;
}
private static void SearchForPairsInSquareRows(SolvingContext context, short[] allSquareIndices)
{
foreach (var rowIndex in Enumerable.Range(0, Consts.SudokuSquareSideSize))
{
var squaresInRow = context.Grid.GetSquaresInRow(rowIndex).ToList();
var sudokuNumbers = GetAllSudokuNumbers();
foreach (var number in sudokuNumbers)
{
var availableColumns = squaresInRow
.Select((x, i) => new NumberInRow
{
Value = number,
Rows =
x.Where(c => c.CanPutCandidate(number))
.Select(c => c.Y)
.Distinct()
.OrderBy(r => r)
.ToList(),
ColumnIndex = (short)i
})
.Where(x => x.Rows.Count == 2)
.ToList();
if (availableColumns.Count < 2)
{
continue;
}
var pairs = availableColumns.SelectMany(x => availableColumns, Tuple.Create)
.Where(x => x.Item1.Value == x.Item2.Value)
.Where(x => x.Item1.ColumnIndex != x.Item2.ColumnIndex)
.ToList();
foreach (var pair in pairs)
{
if (!pair.Item1.Rows.SequenceEqual(pair.Item2.Rows))
{
continue;
}
var remainingSquareIndex = allSquareIndices
.Except(pair.ToList().Select(x => x.ColumnIndex))
.Single();
var remainingSquare = squaresInRow[remainingSquareIndex];
var cellsToRemoveCandidates = remainingSquare.Where(x => pair.Item1.Rows.Contains(x.Y))
.ToList();
foreach (var cell in cellsToRemoveCandidates)
{
context.CellsAffectedWithCrossOut += cell.RemoveCandidates(pair.Item1.Value);
}
}
}
}
}
private static SolvingResult ToSolvingResult(SolvingContext context)
{
return(new SolvingResult
{
IsSuccess = context.IsSuccess,
SudokuGrid = context.Grid,
FilledInCellsCount = context.FilledInCellsCount
});
}
private static SolvingContext CreateContext(IGrid baseGrid)
{
var context = new SolvingContext
{
Grid = baseGrid
};
ResetContext(context);
return(context);
}
public static void SearchForPairsInRows(SolvingContext context)
{
foreach (var rowIndex in Enumerable.Range(0, Consts.SudokuGridSize))
{
var row = context.Grid.GetRow(rowIndex);
var combinations = GetValidPairsCombinations(row);
var pairs = HandleCellPairs(context, combinations, row).ToList();
FindCandidatesPairsInCells(context, row);
}
}
private static void SearchForPairsInColumns(SolvingContext context)
{
foreach (var columnIndex in Enumerable.Range(0, Consts.SudokuGridSize))
{
var column = context.Grid.GetColumn(columnIndex);
var combinations = GetValidPairsCombinations(column);
var pairs = HandleCellPairs(context, combinations, column).ToList();
FindCandidatesPairsInCells(context, column);
}
}
private static void ResetContext(SolvingContext context)
{
context.CellsAffectedWithCrossOut = 0;
context.HasEmptyCells = context.Grid.HasEmptyCells();
context.GoToLoopStart = false;
context.Pairs = new List <Tuple <short, short> >();
if (!context.HasEmptyCells)
{
context.ContinueSolving = false;
}
}
private static void RemoveCandidates(SolvingContext context, ICellGroup cellGroup,
Tuple <ICell, ICell> pair)
{
var otherCells = cellGroup.Except(pair.ToList()).ToList();
var firstFields = pair.Item1.GetCandidates().ToList();
context.Pairs.Add(Tuple.Create(firstFields.First(), firstFields.Last()));
context.PairFound = true;
foreach (var otherCell in otherCells)
{
context.CellsAffectedWithCrossOut += otherCell.RemoveCandidates(firstFields.ToArray());
}
}
private static void SearchForSinglesInContainers(SolvingContext context)
{
SearchSingleNumbersInSquares(context);
foreach (var column in context.Grid.GetColumns())
{
SearchForSingleInGroup(context, column);
}
foreach (var row in context.Grid.GetRows())
{
SearchForSingleInGroup(context, row);
}
}
public void SearchForPairsInSquare_SpecificCase_ShouldFindPair()
{
var grid = SudokuGrids.SpecificCaseForPairInSquare;
var context = new SolvingContext
{
ContinueSolving = true,
Grid = grid
};
SolverService.SearchForPairsInSquares(context);
Assert.True(context.PairFound);
}
public static void SearchSingleNumbersInSquares(SolvingContext context)
{
foreach (var square in context.Grid.GetSquares())
{
SearchForSingleInGroup(context, square);
var notFilledInNumbers = Enumerable.Range(1, 9)
.Select(x => (short)x)
.Except(square.Select(x => x.Value).Distinct())
.ToList();
foreach (var number in notFilledInNumbers)
{
var elligibleCells = square.Where(x => x.CanPutCandidate(number)).ToList();
if (elligibleCells.Count != 2)
{
continue;
}
var first = elligibleCells.First();
var second = elligibleCells.Last();
if (first.X == second.X)
{
var column = context.Grid.GetColumn(first.X);
var pairGroup = new List <ICell> {
first, second
};
var otherCells = column.Except(pairGroup).ToList();
var updatedCells = otherCells.Aggregate(0, (a, b) => a + (b.RemoveCandidate(number) ? 1 : 0));
context.CellsAffectedWithCrossOut += updatedCells;
}
if (first.Y == second.Y)
{
var row = context.Grid.GetRow(first.Y);
var pairGroup = new List <ICell> {
first, second
};
var otherCells = row.Except(pairGroup).ToList();
var updatedCells = otherCells.Aggregate(0, (a, b) => a + (b.RemoveCandidate(number) ? 1 : 0));
context.CellsAffectedWithCrossOut += updatedCells;
}
}
}
}
public static void SearchForPairsInSquareColumns(SolvingContext context, short[] allSquareIndices)
{
foreach (var columnIndex in Enumerable.Range(0, Consts.SudokuSquareSideSize))
{
var squaresInColumn = context.Grid.GetSquaresInColumn(columnIndex).ToList();
var sudokuNumbers = GetAllSudokuNumbers();
foreach (var number in sudokuNumbers)
{
var availableColumns = squaresInColumn
.Select((x, i) => ToNumberInColumn(number, x, i))
.Where(x => x.Columns.Count == 2)
.ToList();
if (availableColumns.Count < 2)
{
continue;
}
var pairs = availableColumns.SelectMany(x => availableColumns, Tuple.Create)
.Where(x => x.Item1.Value == x.Item2.Value)
.Where(x => x.Item1.RowIndex != x.Item2.RowIndex)
.ToList();
foreach (var pair in pairs)
{
if (!pair.Item1.Columns.SequenceEqual(pair.Item2.Columns))
{
continue;
}
var remainingSquareIndex = allSquareIndices
.Except(pair.ToList().Select(x => x.RowIndex))
.Single();
var remainingSquare = squaresInColumn[remainingSquareIndex];
var cellsToRemoveCandidates = remainingSquare.Where(x => pair.Item1.Columns.Contains(x.X))
.ToList();
foreach (var cell in cellsToRemoveCandidates)
{
context.CellsAffectedWithCrossOut += cell.RemoveCandidates(pair.Item1.Value);
}
}
}
}
}
public void SearchSingleNumbersInSquares_SpecificCase_ShouldCrossOut2InFourthRow()
{
var grid = SudokuGrids.SpecificCaseForPairInSquare;
var context = new SolvingContext
{
ContinueSolving = true,
Grid = grid
};
SolverService.SearchSingleNumbersInSquares(context);
var updatedGrid = context.Grid;
var row = updatedGrid.GetRow(3);
var eigthCell = row.GetCell(7);
var ninthCell = row.GetCell(8);
Assert.False(eigthCell.CanPutCandidate(2));
Assert.False(ninthCell.CanPutCandidate(2));
}
public void SearchForPairsInSquareColumns_ForPartaillySolvedHardGridThree_ShouldRemovesTwosInFirstSquare()
{
var grid = SudokuGrids.HardGridThreePartiallySolved;
var context = new SolvingContext
{
ContinueSolving = true,
Grid = grid
};
var allSquareIndices = new short[] { 0, 1, 2 };
SolverService.SearchForPairsInSquareColumns(context, allSquareIndices);
var updatedGrid = context.Grid;
var firstRow = updatedGrid.GetRow(0);
var firstCell = firstRow.GetCell(0);
Assert.False(firstCell.CanPutCandidate(2));
}
public static void SearchForPairsInSquares(SolvingContext context)
{
foreach (var rowIndex in Enumerable.Range(0, Consts.SudokuSquareSideSize))
{
foreach (var columnIndex in Enumerable.Range(0, Consts.SudokuSquareSideSize))
{
var square = context.Grid.GetSquare(columnIndex, rowIndex);
var combinations = GetValidPairsCombinations(square);
var pairs = HandleCellPairs(context, combinations, square).ToList();
ApplyPairsToRowsAndColumns(context, pairs);
FindCandidatesPairsInCells(context, square);
}
}
var allSquareIndices = new short[] { 0, 1, 2 };
SearchForPairsInSquareRows(context, allSquareIndices);
SearchForPairsInSquareColumns(context, allSquareIndices);
}
private static void ApplyPairsToRowsAndColumns(SolvingContext context, IEnumerable <Tuple <ICell, ICell> > pairs)
{
foreach (var pair in pairs)
{
if (pair.Item1.X == pair.Item2.X)
{
var colIndex = pair.Item1.X;
var column = context.Grid.GetColumn(colIndex);
RemoveCandidates(context, column, pair);
}
if (pair.Item1.Y == pair.Item2.Y)
{
var rowIdx = pair.Item2.Y;
var row = context.Grid.GetRow(rowIdx);
RemoveCandidates(context, row, pair);
}
}
}
private static bool SearchForPairs(SolvingContext context)
{
context.TargetCell = context.Grid.GetCellWithLeastAvailableValues();
if (context.TargetCell == null || context.TargetCell.GetCandidates().Count <= 1)
{
return(false);
}
SearchForPairsInRows(context);
SearchForPairsInColumns(context);
SearchForPairsInSquares(context);
if (context.PairFound && context.CellsAffectedWithCrossOut > 0)
{
return(true);
}
context.IsSuccess = false;
context.ContinueSolving = false;
return(true);
}
private static IEnumerable <Tuple <ICell, ICell> > HandleCellPairs(SolvingContext context,
IEnumerable <Tuple <ICell, ICell> > combinations, ICellGroup cellGroup)
{
foreach (var combination in combinations)
{
if (combination.Item1 == null || combination.Item2 == null)
{
break;
}
var firstFields = combination.Item1.GetCandidates().ToList();
var secondFields = combination.Item2.GetCandidates().ToList();
if (firstFields.Count != 2 || secondFields.Count != 2 ||
!firstFields.SequenceEqual(secondFields))
{
continue;
}
RemoveCandidates(context, cellGroup, combination);
yield return(combination);
}
}