internal ConstraintHeader CopyToMatrix(ExactCoverMatrix matrix)
{
Debug.Assert(FirstLink != null, $"Can't copy a header with a null {nameof(FirstLink)}.");
Debug.Assert(!IsSatisfied, $"Can't copy a header that's already satisfied.");
var copy = new ConstraintHeader(matrix);
foreach (Link?link in GetLinks())
{
Square?square = matrix.GetSquare(link.PossibleSquare.Square.Coordinate);
Debug.Assert(square != null,
$"Tried to copy a square link for a null square at {link.PossibleSquare.Square.Coordinate}.");
PossibleValue?possibleSquare = square.GetPossibleValue(link.PossibleSquare.ValueIndex);
Debug.Assert(possibleSquare != null, "Tried to link header to null possible square value.");
_ = Link.CreateConnectedLink(possibleSquare, copy);
}
return(copy);
}
public static ConstraintHeader CreateConnectedHeader(
ExactCoverMatrix matrix, ReadOnlySpan <PossibleValue> possibleSquares)
{
var header = new ConstraintHeader(matrix);
matrix.Attach(header);
foreach (PossibleValue?possibleSquare in possibleSquares)
{
_ = Link.CreateConnectedLink(possibleSquare, header);
}
if (header.Count == 0)
{
throw new ArgumentException(
$"Must provide at least one {nameof(PossibleValue)} when creating a {nameof(ConstraintHeader)}.");
}
return(header);
}
internal ConstraintHeader(ExactCoverMatrix matrix)
{
Matrix = matrix;
NextHeader = PreviousHeader = this;
}
