///<summary>
/// RotateLeft
/// Rebalance the tree by rotating the nodes to the right
///</summary>
public void RotateRight(BinarySearchNode x)
{
if (!x.IsSentinel && !x.Left.IsSentinel)
{
BinarySearchNode y = x.Left;
x.Left = y.Right;
if (!y.Right.IsSentinel)
{
y.Right.Parent = x;
}
y.Parent = x.Parent;
if (x.Parent != null)
{
if (x == x.Parent.Left)
{
x.Parent.Left = y;
}
else
{
x.Parent.Right = y;
}
}
else
{
this.Root = y;
}
y.Right = x;
x.Parent = y;
}
}
private RedBlackColors GetColor(BinarySearchNode node)
{
if ((node == null) || (node.IsSentinel))
{
return(RedBlackColors.Black);
}
return((node as RedBlackNode).Color);
}
protected override void OnItemDeleted(BinarySearchNode deleted, BinarySearchNode location)
{
if (this.IsBlack(deleted))
{
bool isleft = location.IsSentinel ? deleted.Parent.Left.IsSentinel : location.IsLeftChild;
this.OnItemDeletedInternal(isleft, location, deleted.Parent, isleft ? deleted.Parent.Right : deleted.Parent.Left);
}
base.OnItemDeleted(deleted, location);
}
private BinarySearchNode(bool isSentinel) {
if(isSentinel) {
this.rbnLeft = this.rbnParent = this.rbnRight = null;
this.objData = null;
this.ordKey = null;
} else {
this.rbnLeft = this.rbnRight = BinarySearchNode.Sentinel;
this.rbnParent = null;
this.objData = null;
this.ordKey = null;
}
}
private void OnItemInsertedInternal(BinarySearchNode token)
{
if (token.Parent != null) //case 1: the new node is the root
{
if (this.IsRed(token.Parent)) //case 2: the new nodes parent is black
//Since root must be black, and parent is red, grandparent must exist
//and grandparent must be black since no two reds are touching
{
if (this.IsRed(token.Parent.Sibling))
{
this.SetColor(token.Parent.Sibling, RedBlackColors.Black);
this.SetColor(token.Parent, RedBlackColors.Black);
this.SetColor(token.Parent.Parent, RedBlackColors.Red);
this.OnItemInsertedInternal(token.Parent.Parent);
}
else
{
if (token.IsRightChild && token.Parent.IsLeftChild)
{
this.RotateLeft(token.Parent);
token = token.Left;
}
else if (token.IsLeftChild && token.Parent.IsRightChild)
{
this.RotateRight(token.Parent);
token = token.Right;
}
this.SetColor(token.Parent, RedBlackColors.Black);
this.SetColor(token.Parent.Parent, RedBlackColors.Red);
if (token.IsLeftChild && token.Parent.IsLeftChild)
{
this.RotateRight(token.Parent.Parent);
}
else
{
this.RotateLeft(token.Parent.Parent);
}
}
}
}
else
{
this.SetColor(token, RedBlackColors.Black);
}
}
/*private void IsColor(BinarySearchNode node, RedBlackColors color) {
* if(color == RedBlackColors.Black)
* return this.IsBlack(node);
* return this.IsRed(node);
* }*/
private void SetColor(BinarySearchNode node, RedBlackColors color)
{
(node as RedBlackNode).Color = color;
}
private bool IsRed(BinarySearchNode node)
{
return(this.GetColor(node) == RedBlackColors.Red);
}
protected override void OnItemInserted(BinarySearchNode node)
{
this.OnItemInsertedInternal(node);
base.OnItemInserted(node);
}
private void OnItemDeletedInternal(bool isleft, BinarySearchNode token, BinarySearchNode parent, BinarySearchNode sibling)
{
if ((parent == null) || this.IsRed(token))
{
if (!token.IsSentinel)
{
this.SetColor(token, RedBlackColors.Black);
}
}
else
{
//token can be sentinel
if (this.IsRed(sibling))
{
this.SetColor(sibling, RedBlackColors.Black);
this.SetColor(parent, RedBlackColors.Red);
if (isleft)
{
this.RotateLeft(parent);
}
else
{
this.RotateRight(parent);
}
this.OnItemDeletedInternal(isleft, token, parent, isleft ? parent.Right : parent.Left);
} /*else if(token.Sibling.IsSentinel) {
* this.OnItemDeletedInternal(token.Parent);
* }*/
else
{
BinarySearchNode near = isleft ? sibling.Left : sibling.Right;
BinarySearchNode far = isleft ? sibling.Right : sibling.Left;
if (this.IsBlack(near) && this.IsBlack(far))
{
//this holds if both near and far are sentinels
//after this, there has to be a red nephew
//I am having problem with token.sibling being sentinel
this.SetColor(sibling, RedBlackColors.Red);
this.OnItemDeletedInternal(parent.IsLeftChild, parent, parent.Parent, parent.Sibling);
}
else if (this.IsRed(near) && this.IsBlack(far))
{
this.SetColor(near, RedBlackColors.Black);
this.SetColor(sibling, RedBlackColors.Red);
if (isleft)
{
this.RotateRight(sibling);
}
else
{
this.RotateLeft(sibling);
}
this.OnItemDeletedInternal(isleft, token, parent, isleft ? parent.Right : parent.Left);
}
else
{
this.SetColor(sibling, this.GetColor(parent));
this.SetColor(parent, RedBlackColors.Black);
this.SetColor(far, RedBlackColors.Black);
if (isleft)
{
this.RotateLeft(parent);
}
else
{
this.RotateRight(parent);
}
}
}
}
/*if(token.IsRoot || this.IsRed(token)) {
* if(!token.IsSentinel)
* this.SetColor(token, RedBlackColors.Black);
* } else if(token.Sibling.IsSentinel) {
* this.OnItemDeletedInternal(token.Parent);
* } else if(this.IsRed(token.Sibling)) {
* this.SetColor(token.Sibling, RedBlackColors.Black);
* this.SetColor(token.Parent, RedBlackColors.Red);
* if(token.IsLeftChild)
* this.RotateLeft(token.Parent);
* else
* this.RotateRight(token.Parent);
* this.OnItemDeletedInternal(token);
* } else if(this.IsBlack(token.Sibling)) {
* BinarySearchNode nearNephew = token.IsRightChild ? token.Sibling.Right : token.Sibling.Left;
* BinarySearchNode farNephew = token.IsRightChild ? token.Sibling.Left : token.Sibling.Right;
* if(this.IsBlack(nearNephew) && this.IsBlack(farNephew)) {
* //this holds if both near and far are sentinels
* //after this, there has to be a red nephew
* this.SetColor(token.Sibling, RedBlackColors.Red);
* this.OnItemDeletedInternal(token.Parent);
* } else if(nearNephew.IsSentinel || farNephew.IsSentinel) {
* this.SetColor(farNephew.IsSentinel ? nearNephew : farNephew, RedBlackColors.Black);
* if(token.IsLeftChild)
* this.RotateLeft(token.Parent);
* else
* this.RotateRight(token.Parent);
* } else {
* //black sibling, at least one red nephew
* if(this.IsBlack(farNephew)) {
* this.SetColor(token.Sibling, RedBlackColors.Red);
* this.SetColor(nearNephew, RedBlackColors.Black);
* if(token.IsLeftChild)
* this.RotateRight(token.Sibling);
* else
* this.RotateLeft(token.Sibling);
* }
* this.SetColor(farNephew, RedBlackColors.Black);
* if(token.IsLeftChild)
* this.RotateLeft(token.Parent);
* else
* this.RotateRight(token.Parent);
* }
* }
*/
//since the item deleted and its child were black, in order
//for the same number of black nodes along any path to leaf,
//the the token(node that took over for the deleted node)
//must have a sibling and the sibling must have two children
/*RedBlackNode parent = token.Parent as RedBlackNode;
* RedBlackNode sibling = token.Sibling as RedBlackNode;
*
* if(sibling.Color == RedBlackColors.Red) {
* parent.Color = RedBlackColors.Red;
* sibling.Color = RedBlackColors.Black;
* if(token.IsLeftChild)
* this.RotateLeft(parent);
* else
* this.RotateRight(parent);
* }
*
* RedBlackNode nephew1 = sibling.Left as RedBlackNode;
* RedBlackNode nephew2 = sibling.Right as RedBlackNode;
* if ((parent.Color == RedBlackColors.Black) &&
* sibling.Color == RedBlackColors.Black &&
* nephew1.Color == RedBlackColors.Black &&
* nephew2.Color == RedBlackColors.Black) {
* sibling.Color = RedBlackColors.Red;
* this.OnItemDeletedInternal(parent);
* } else {
* if ((parent.Color == RedBlackColors.Red) &&
* (sibling.Color == RedBlackColors.Black) &&
* (nephew1.Color == RedBlackColors.Black) &&
* (nephew2.Color == RedBlackColors.Black)) {
* sibling.Color = RedBlackColors.Red;
* parent.Color = RedBlackColors.Black;
* } else {
* if (token.IsLeftChild &&
* (sibling.Color == RedBlackColors.Black) &&
* (nephew1.Color == RedBlackColors.Red) &&
* (nephew2.Color == RedBlackColors.Black)) {
* sibling.Color = RedBlackColors.Red;
* nephew1.Color = RedBlackColors.Black;
* this.RotateRight(sibling);
* } else if (token.IsRightChild &&
* (sibling.Color == RedBlackColors.Black) &&
* (nephew2.Color == RedBlackColors.Red) &&
* (nephew1.Color == RedBlackColors.Black)) {
* sibling.Color = RedBlackColors.Red;
* nephew2.Color = RedBlackColors.Black;
* this.RotateLeft(sibling);
* }
* sibling.Color = parent.Color;
* parent.Color = RedBlackColors.Black;
* if (token.IsLeftChild) {
* nephew2.Color = RedBlackColors.Black;
* this.RotateLeft(parent);
* } else {
* nephew1.Color = RedBlackColors.Black;
* this.RotateRight(parent);
* }
* }
* }
* }*/
}
static BinarySearchNode() {
sentinel = new BinarySearchNode(true);
}