/// <inheritdoc/>
public void Constrain(IReadOnlyPuzzle puzzle, ExactCoverMatrix matrix)
{
Span <bool> isConstraintSatisfiedAtIndex =
stackalloc bool[matrix.AllPossibleValues.Length];
for (int row = 0; row < puzzle.Size; row++)
{
ReadOnlySpan <Square?> rowSquares = matrix.GetSquaresOnRow(row);
isConstraintSatisfiedAtIndex.Clear();
for (int col = 0; col < puzzle.Size; col++)
{
int?puzzleValue = puzzle[row, col];
if (puzzleValue.HasValue)
{
isConstraintSatisfiedAtIndex[matrix.ValuesToIndices[puzzleValue.Value]] = true;
}
}
for (int valueIndex = 0; valueIndex < isConstraintSatisfiedAtIndex.Length; valueIndex++)
{
if (isConstraintSatisfiedAtIndex[valueIndex])
{
ConstraintUtil.DropPossibleSquaresForValueIndex(rowSquares, valueIndex, matrix);
continue;
}
ConstraintUtil.AddConstraintHeadersForValueIndex(rowSquares, valueIndex, matrix);
}
}
}
public void TryRemoveFromConstraint_OnSuccess()
{
var puzzle = new Puzzle(4);
var matrix = new ExactCoverMatrix(puzzle);
var constraintHeader = ConstraintHeader.CreateConnectedHeader(
matrix,
matrix.GetSquaresOnRow(0).ToArray().Select(s => s.AllPossibleValues[0]).ToArray());
Link firstLink = constraintHeader.FirstLink;
Link secondLink = firstLink.Down;
Link thirdLink = secondLink.Down;
Link fourthLink = thirdLink.Down;
Assert.True(firstLink.TryRemoveFromConstraint());
Assert.Same(fourthLink, firstLink.Up);
Assert.Same(secondLink, firstLink.Down);
Assert.Same(secondLink, constraintHeader.FirstLink);
Assert.Same(fourthLink, secondLink.Up);
Assert.Same(secondLink, fourthLink.Down);
Assert.Equal(3, constraintHeader.Count);
}
public void TryRemoveFromConstraint_WhenConstraintSatisfied_LeavesUnchanged()
{
var puzzle = new Puzzle(4);
var matrix = new ExactCoverMatrix(puzzle);
var constraintHeader = ConstraintHeader.CreateConnectedHeader(
matrix,
matrix.GetSquaresOnRow(0).ToArray().Select(s => s.AllPossibleValues[0]).ToArray());
Link firstLink = constraintHeader.FirstLink;
Link secondLink = firstLink.Down;
Link thirdLink = secondLink.Down;
Link fourthLink = thirdLink.Down;
int expectedConstraintCount = constraintHeader.Count;
Assert.True(firstLink.TrySatisfyConstraint());
Assert.True(secondLink.TryRemoveFromConstraint());
Assert.Equal(expectedConstraintCount, constraintHeader.Count);
Assert.Same(firstLink, secondLink.Up);
Assert.Same(secondLink, firstLink.Down);
Assert.Same(secondLink, thirdLink.Up);
Assert.Same(thirdLink, secondLink.Down);
}
