public DancingLinksNode(DancingLinksHeader header, int row)
{
Header = header;
Left = this;
Right = this;
Up = this;
Down = this;
RowID = row;
}
public DancingLinks(int[][] matrix)
{
_control = new DancingLinksHeader
{
Header = null,
Up = null,
Down = null
};
for (int c = 0; c < matrix[0].Length; c++)
{
var header = new DancingLinksHeader
{
Left = _control.Left,
Right = _control
};
header.Left.Right = header;
header.Right.Left = header;
}
for (int i = 0; i < matrix.Length; i++)
{
DancingLinksHeader header = _control.Right as DancingLinksHeader;
DancingLinksNode last = null;
for (int j = 0; j < matrix[i].Length; j++, header = header.Right as DancingLinksHeader)
{
if (matrix[i][j] == 0)
{
continue;
}
var tmp = new DancingLinksNode(header, i);
if (last != null)
{
tmp.Left = last;
tmp.Right = last.Right;
tmp.Left.Right = tmp;
tmp.Right.Left = tmp;
}
tmp.Up = header.Up;
tmp.Down = header;
tmp.Up.Down = tmp;
tmp.Down.Up = tmp;
header.Count++;
last = tmp;
}
}
}
private DancingLinksHeader GetNextColumn()
{
DancingLinksHeader header = null;
int min = int.MaxValue;
for (var tmp = _control.Right as DancingLinksHeader; tmp != _control; tmp = tmp.Right as DancingLinksHeader)
{
if (min > tmp.Count)
{
min = tmp.Count;
header = tmp;
}
}
return(header);
}
private bool Search(List <int> solution)
{
if (_control.Right == _control)
{
var args = new SolutionFoundEventArgs(solution);
SolutionFound(this, args);
return(args.Terminate);
}
DancingLinksHeader header = GetNextColumn();
Cover(header);
for (DancingLinksNode node = header.Down; node != header; node = node.Down)
{
solution.Add(node.RowID);
for (DancingLinksNode tmp = node.Right; tmp != node; tmp = tmp.Right)
{
Cover(tmp);
}
if (Search(solution))
{
return(true);
}
solution.RemoveAt(solution.Count - 1);
for (DancingLinksNode tmp = node.Right; tmp != node; tmp = tmp.Right)
{
Uncover(tmp);
}
}
Uncover(header);
return(false);
}