private void RightLeftRotate(AVLTreeNode <T> parent)
{
//parent must have a right child and a right-left grandchild
RightRotate(parent.rightChild);
LeftRotate(parent);
}
private void LeftRightRotate(AVLTreeNode <T> parent)
{
//parent must have a left child and a left-right grandchild
LeftRotate(parent.leftChild);
RightRotate(parent);
}
private bool RemoveCurrentNode(AVLTreeNode <T> node, bool isLeft, bool removeAll = false)
{
if (node.weight > 1)
{
if (removeAll)
{
for (int i = 0; i < node.weight - 1; i++)
{
node.weight--;
MinusParentChildrenNum(node);
}
}
else
{
node.weight--;
MinusParentChildrenNum(node);
return(true);
}
}
if (node.leftChild == null)
{
var parent = node.parent;
if (node.rightChild != null)
{
node.rightChild.parent = parent;
}
if (parent == null)
{
//root node
root = node.rightChild;
}
else
{
if (isLeft)
{
parent.leftChild = node.rightChild;
}
else
{
parent.rightChild = node.rightChild;
}
}
MinusParentChildrenNum(node);
BalanceNode(node.parent);
node = null;//Memory Leak??
}
else if (node.rightChild == null)
{
var parent = node.parent;
if (node.leftChild != null)
{
node.leftChild.parent = parent;
}
if (parent == null)
{
//root node
root = node.leftChild;
}
else
{
if (isLeft)
{
parent.leftChild = node.leftChild;
}
else
{
parent.rightChild = node.leftChild;
}
}
MinusParentChildrenNum(node);
BalanceNode(node.parent);
node = null;
}
else
{
//Get the next node in InOrderTraverse
var nextNode = GetNextInOrderNode(node);
if (nextNode.parent == node)
{
if (node.parent == null)
{
//root node
root = nextNode;
nextNode.parent = null;
}
else
{
var parent = node.parent;
nextNode.parent = parent;
if (isLeft)
{
parent.leftChild = nextNode;
}
else
{
parent.rightChild = nextNode;
}
}
nextNode.leftChild = node.leftChild;
if (node.leftChild != null)
{
node.leftChild.parent = nextNode;
nextNode.childrenNum += node.leftChild.childrenNum + node.leftChild.weight;
}
MinusParentChildrenNum(nextNode);
BalanceNode(nextNode);
node = null;
}
else
{
//Copy the value of nextNode to currentNode, then delete nextNode
node.data = nextNode.data;
node.weight = nextNode.weight;
nextNode.parent.leftChild = nextNode.rightChild;
if (nextNode.rightChild != null)
{
nextNode.rightChild.parent = nextNode.parent;
}
MinusParentChildrenNum(nextNode, node, nextNode.weight);
UpdateChildrenNumberByDirectChildren(node);
BalanceNode(nextNode.parent);
nextNode = null;
}
}
return(true);
}
private void BalanceNode(AVLTreeNode <T> newNode)
{
if (newNode == null)
{
return;
}
var currentNode = newNode;
var parent = newNode;
var isChildLeft = true;
var isGrandchildLeft = true;
while (parent != null)
{
if (parent.leftChild == currentNode)
{//Left Child
parent.leftHeight = Math.Max(currentNode.leftHeight, currentNode.rightHeight) + 1;
}
else if (parent.rightChild == currentNode)
{//Right Child
parent.rightHeight = Math.Max(currentNode.leftHeight, currentNode.rightHeight) + 1;
}
else
{//First time
if (parent.leftChild != null)
{
parent.leftHeight = Math.Max(parent.leftChild.leftHeight, parent.leftChild.rightHeight) + 1;
}
else
{
parent.leftHeight = 0;
}
if (parent.rightChild != null)
{
parent.rightHeight = Math.Max(parent.rightChild.leftHeight, parent.rightChild.rightHeight) + 1;
}
else
{
parent.rightHeight = 0;
}
}
var diff = parent.leftHeight - parent.rightHeight;
if (diff >= 2 || diff <= -2)
{
if (parent.leftHeight > parent.rightHeight)
{
isChildLeft = true;
//The balance of sub tree may be 0 on a deletion. Do not double-rotate in this case.
if (parent.leftChild.leftHeight >= parent.leftChild.rightHeight)
{
isGrandchildLeft = true;
}
else
{
isGrandchildLeft = false;
}
}
else
{
isChildLeft = false;
if (parent.rightChild.leftHeight > parent.rightChild.rightHeight)
{
isGrandchildLeft = true;
}
else
{
isGrandchildLeft = false;
}
}
Rotate(parent, isChildLeft, isGrandchildLeft);
}
currentNode = parent;
parent = parent.parent;
}
}
//O(LogN)
public bool InsertNode(T data)
{
try
{
var newNode = new AVLTreeNode <T>()
{
data = data
};
if (root == null)
{
root = newNode;
return(true);
}
var currentNode = root;
while (true)
{
var compareResult = CompareNode(data, currentNode.data);
if (compareResult > 0)
{
currentNode.childrenNum++;
if (currentNode.rightChild == null)
{
currentNode.rightChild = newNode;
newNode.parent = currentNode;
break;
}
else
{
currentNode = currentNode.rightChild;
}
}
else if (compareResult < 0)
{
currentNode.childrenNum++;
if (currentNode.leftChild == null)
{
currentNode.leftChild = newNode;
newNode.parent = currentNode;
break;
}
else
{
currentNode = currentNode.leftChild;
}
}
else
{
currentNode.weight++;
return(true);
}
}
BalanceNode(newNode);
return(true);
}
catch (Exception ex)
{
Console.WriteLine(ex.ToString());
}
return(false);
}
