/*******************************************************************************************/
/*******************************************************************************************/
private void DeleteNodeLeaf(Node node)
{
if (node.Color == NodeColor.RED)
{
DetachNode(node);
}
else
{
NodeDoubleBlack nodeDB = new NodeDoubleBlack(node.Parent, node, null);
DetachNode(node);
FixDoubleBlackNode(nodeDB);
}
}
/*******************************************************************************************/
/*******************************************************************************************/
private void FixDoubleBlackNode(NodeDoubleBlack nodeDB)
{
if (nodeDB.Parent is null)
{
return;
}
Node sibling = nodeDB.Sibling;
if (sibling != null && sibling.Color == NodeColor.BLACK && HasRedNode(sibling))
{
Node siblingRedChild = HasLeftNodeRed(sibling) ? sibling.Left : sibling.Right;
if (sibling < sibling.Parent &&
(HasBothNodesRed(sibling) || HasLeftNodeRed(sibling)))
{
// Left Left case
SetNodeColor(sibling.Left, NodeColor.BLACK);
SwapColors(sibling, sibling.Parent);
RotateNode(sibling);
}
else if (sibling < sibling.Parent && siblingRedChild > sibling)
{
// Left Right Case
SwapColors(siblingRedChild, sibling);
RotateNode(siblingRedChild);
RotateNode(siblingRedChild);
}
else if ((sibling > sibling.Parent && siblingRedChild > sibling) ||
HasBothNodesRed(sibling))
{
// Right Right Case
RotateNode(sibling);
SwapColors(sibling, sibling.Parent);
}
else if (sibling > sibling.Parent && HasLeftNodeRed(sibling))
{
// Left Right Case
RotateNode(sibling.Left);
RotateNode(sibling.Left);
}
}
else if (sibling is null ||
(sibling.Color == NodeColor.BLACK && HasBothNodesBlack(sibling)))
{
// Recolour
if (nodeDB.Parent.Color == NodeColor.BLACK && sibling != null)
{
SetNodeColor(sibling, NodeColor.RED);
}
}
/*******************************************************************************************/
/*******************************************************************************************/
private void DeleteNodeWithOneChild(Node node)
{
Node child = node.Left is null ? node.Right : node.Left;
if (node.Color == NodeColor.RED || child.Color == NodeColor.RED)
{
SetNodeColor(child, NodeColor.BLACK);
DetachNode(node);
}
else
{
NodeDoubleBlack nodeDB = new NodeDoubleBlack(node.Parent, node, child);
DetachNode(node);
FixDoubleBlackNode(nodeDB);
}
}
/*******************************************************************************************/
/*******************************************************************************************/
private void DeleteNodeWithBothChildren(Node node)
{
Node leastSuccessor = FindLowestNode(node.Right);
Node leastSuccessorChild = leastSuccessor.Right is null ? null : leastSuccessor.Right;
if (leastSuccessor.Color == NodeColor.RED ||
(leastSuccessorChild != null && leastSuccessorChild.Color == NodeColor.RED))
{
if (leastSuccessorChild != null)
{
SetNodeColor(leastSuccessorChild, NodeColor.BLACK);
}
SwapColors(node, leastSuccessor);
DetachNode(node);
}
else
{
NodeDoubleBlack nodeDB = new NodeDoubleBlack(leastSuccessor.Parent, leastSuccessor, leastSuccessorChild);
SwapColors(node, leastSuccessor);
DetachNode(node);
FixDoubleBlackNode(nodeDB);
}
}
