public DancingLinksNode(DancingLinksColumnHeader h, int cellx, int celly, int cellnum)
{
row = new Triple <int>(cellx, celly, cellnum);
header = h;
}
public bool dancingLinksAlg()
{
if (columns.Count == 0)
{
return(true);
}
int minCount = columns.Min(x => x.columnMemberCount);
if (minCount <= 0)
{
return(false);
}
DancingLinksColumnHeader c = columns.Where(x => x.columnMemberCount == minCount).ToArray()[0];
int count = c.columnMemberCount;
DancingLinksNode curNode = c.firstEntry;
//Outer loop iterates through rows intersecting the column
//Inside this, we look at a given row. Iterate through the columns intersecting that row.
while (count > 0)
{
#region Removal_and_Test
DancingLinksNode curColPivot = curNode.right;
while (curColPivot != curNode)
{
DancingLinksNode curRowPivot = curColPivot.down;
while (curRowPivot != curColPivot)
{
#region Remove_rows_Except_Pivot_Row
DancingLinksNode curRemNode = curRowPivot.right;
while (curRemNode != curRowPivot)
{
curRemNode.up.down = curRemNode.down;
curRemNode.down.up = curRemNode.up;
curRemNode.header.columnMemberCount--;
curRemNode = curRemNode.right;
}
rows.Remove(rowLookUp[curRowPivot.row]);
#endregion
//curRowPivot.right.left = curRowPivot.left;
//curRowPivot.left.right = curRowPivot.right;
curRowPivot = curRowPivot.down;
}
columns.Remove(curColPivot.header);
//We must remove the Pivot Row as well.
//Notice that we do not remove the Pivot Row from the rows list. This is intentional.
curColPivot.up.down = curColPivot.down;
curColPivot.down.up = curColPivot.up;
curColPivot = curColPivot.right;
}
//Lastly, we remove the pivot column.
columns.Remove(curNode.header);
curNode.left.right = curNode.right;
curNode.right.left = curNode.left;
DancingLinksNode colRemNode = curNode.down;
while (colRemNode != curNode)
{
colRemNode.left.right = colRemNode.right;
colRemNode.right.left = colRemNode.left;
colRemNode = colRemNode.down;
}
if (dancingLinksAlg())
{
return(true);
}
#endregion
#region Readd
else
{
//If removing this row didn't work, backtrack and undo all those row and column removals.
columns.Add(curNode.header);
curNode.right.left = curNode;
curNode.left.right = curNode;
DancingLinksNode colAddNode = curNode.down;
while (colAddNode != curNode)
{
colAddNode.left.right = colAddNode.right;
colAddNode.right.left = colAddNode.left;
colAddNode = colAddNode.down;
}
//Now, we follow the links into the inner rows and columns to restore them as well.
curColPivot = curNode.right;
while (curColPivot != curNode)
{
DancingLinksNode curRowPivot = curColPivot.down;
while (curRowPivot != curColPivot)
{
#region Add_rows_Except_Pivot_Row
DancingLinksNode curAddNode = curRowPivot.right;
while (curAddNode != curRowPivot)
{
curAddNode.up.down = curAddNode;
curAddNode.down.up = curAddNode;
curAddNode.header.columnMemberCount++;
curAddNode = curAddNode.right;
}
rows.Add(rowLookUp[curRowPivot.row]);
#endregion
//curRowPivot.right.left = curRowPivot.left;
//curRowPivot.left.right = curRowPivot.right;
curRowPivot = curRowPivot.down;
}
columns.Add(curColPivot.header);
//We must Add the Pivot Row as well.
curColPivot.up.down = curColPivot;
curColPivot.down.up = curColPivot;
curColPivot = curColPivot.right;
}
}
#endregion
curNode = curNode.down;
count--;
}
return(false);
}
