public void Return_UndoesDrop()
{
var puzzle = new Puzzle(4);
var matrix = new ExactCoverMatrix(puzzle);
new RowUniquenessConstraint().Constrain(puzzle, matrix);
new ColumnUniquenessConstraint().Constrain(puzzle, matrix);
int valueIndex = 0;
Square square = matrix.GetSquare(new Coordinate(0, 0));
PossibleValue possibleValue = square.GetPossibleValue(valueIndex);
Link linkA = possibleValue.FirstLink;
Link linkB = linkA.Right;
Assert.True(possibleValue.TryDrop());
possibleValue.Return();
Assert.Equal(4, square.NumPossibleValues);
Assert.Equal(PossibleSquareState.UNKNOWN, possibleValue.State);
ConstraintHeader constraintA = linkA.Constraint;
ConstraintHeader constraintB = linkB.Constraint;
Assert.Equal(4, constraintA.Count);
Assert.Equal(4, constraintB.Count);
Assert.Contains(linkA, constraintA.GetLinks());
Assert.Contains(linkB, constraintB.GetLinks());
}
public void TryDrop_LeavesUnchangedOnFailure()
{
var puzzle = new Puzzle(4);
var matrix = new ExactCoverMatrix(puzzle);
new RowUniquenessConstraint().Constrain(puzzle, matrix);
new ColumnUniquenessConstraint().Constrain(puzzle, matrix);
int valueIndex = 0;
Assert.True(matrix.GetSquare(new Coordinate(0, 0)).GetPossibleValue(valueIndex).TryDrop());
Assert.True(matrix.GetSquare(new Coordinate(0, 1)).GetPossibleValue(valueIndex).TryDrop());
Assert.True(matrix.GetSquare(new Coordinate(0, 2)).GetPossibleValue(valueIndex).TryDrop());
Square square = matrix.GetSquare(new Coordinate(0, 3));
PossibleValue possibleValue = square.GetPossibleValue(valueIndex);
Link linkA = possibleValue.FirstLink;
Link linkB = linkA.Right;
ConstraintHeader constraintA = linkA.Constraint;
ConstraintHeader constraintB = linkB.Constraint;
Assert.False(possibleValue.TryDrop());
Assert.Equal(4, square.NumPossibleValues);
Assert.Equal(PossibleSquareState.UNKNOWN, possibleValue.State);
Assert.Equal(1, constraintA.Count);
Assert.Equal(4, constraintB.Count);
Assert.Same(linkA, constraintA.FirstLink);
Assert.Contains(linkB, constraintB.GetLinks());
}
public void TryDrop_DropsOnSuccess()
{
var puzzle = new Puzzle(4);
var matrix = new ExactCoverMatrix(puzzle);
new RowUniquenessConstraint().Constrain(puzzle, matrix);
new ColumnUniquenessConstraint().Constrain(puzzle, matrix);
int valueIndex = 1;
Square square = matrix.GetSquare(new Coordinate(1, 0));
PossibleValue possibleValue = square.GetPossibleValue(valueIndex);
Link linkA = possibleValue.FirstLink;
Link linkB = linkA.Right;
ConstraintHeader constraintA = linkA.Constraint;
ConstraintHeader constraintB = linkB.Constraint;
Assert.True(possibleValue.TryDrop());
Assert.Equal(3, square.NumPossibleValues);
Assert.Equal(PossibleSquareState.DROPPED, possibleValue.State);
Assert.Equal(3, constraintA.Count);
Assert.Equal(3, constraintB.Count);
Assert.DoesNotContain(linkA, constraintA.GetLinks());
Assert.DoesNotContain(linkB, constraintB.GetLinks());
}