private void ScanRegion(RegionQueue regions, MutablePuzzle puzzle, Region region)
{
var placedDigits = region.GetPlacedDigits();
for (int i = 1; i <= Puzzle.LineLength; i++)
{
var digit = SudokuValues.FromHumanValue(i);
if (placedDigits.HasAnyOptions(digit))
{
continue;
}
var positions = region.GetPositions(digit);
if (positions.IsSingle)
{
var index = positions.ToIndex();
var coords = region.GetCoordinate(index);
var update = new CellUpdate(digit.Invert(), coords);
puzzle.RemoveOptions(update);
regions.Enqueue(RegionType.Row, coords.Row);
regions.Enqueue(RegionType.Column, coords.Column);
regions.Enqueue(RegionType.Box, coords.Box);
}
}
}
private void ScanRegion(RegionQueue regions, MutablePuzzle puzzle, Region region)
{
var placedDigits = region.GetPlacedDigits();
for (int i = 0; i < Puzzle.LineLength; i++)
{
var cell = region[i];
if (!cell.IsSingle && cell.HasAnyOptions(placedDigits))
{
var coords = region.GetCoordinate(i);
puzzle.RemoveOptions(coords, placedDigits);
var newCell = cell.RemoveOptions(placedDigits);
if (newCell.IsSingle)
{
// since we have placed a digit we must
// scan these regions again
regions.Enqueue(RegionType.Row, coords.Row);
regions.Enqueue(RegionType.Column, coords.Column);
regions.Enqueue(RegionType.Box, coords.Box);
}
}
}
}
public void Apply(MutablePuzzle puzzle, RegionQueue changedRegions)
{
if (++depth > 10)
{
return;
}
while (changedRegions.TryDequeue(puzzle, out var region))
{
for (int i = 0; i < Puzzle.LineLength; i++)
{
var value = region[i];
var coords = region.GetCoordinate(i);
if (value.GetOptionCount() != 2)
{
continue;
}
// if there are are only 2 bits set, bitwise and
// with the value - 1 will return the highest option
var highestValue = new SudokuValues(value.Values & (value.Values - 1));
#if DEBUG
Program.Debugger.AddAction($"Attempting {highestValue.Invert().Intersect(value)} in {coords}");
#endif
var oldSolver = _solver;
var changeset = new SingleCellChangeSet(new CellUpdate(highestValue, coords));
var newSolver = new Solver(changeset, _solver);
_solver = newSolver;
var(result, _) = newSolver.Solve();
_solver = oldSolver;
#if DEBUG
Program.Debugger.AddAction($"Result: {result}");
#endif
switch (result)
{
case SolveResult.Success:
puzzle.Absorb(newSolver.Puzzle);
return;
case SolveResult.Invalid:
// we picked the wrong digit
puzzle.RemoveOptions(new CellUpdate(highestValue.Invert(), coords));
return;
}
}
}
}
public void ApplyToPuzzle(MutablePuzzle puzzle)
{
puzzle.RemoveOptions(_update);
}