internal AVLTreeNode(AVLTreeNode <T> parent, T value)
{
Parent = parent;
Value = value;
Height = 0;
}
//O(log(n)) always
private void delete(AVLTreeNode <T> node, T value)
{
var baseCase = false;
var compareResult = node.Value.CompareTo(value);
//node is less than the search value so move right to find the deletion node
if (compareResult < 0)
{
if (node.Right == null)
{
throw new Exception("Item do not exist");
}
delete(node.Right, value);
}
//node is less than the search value so move left to find the deletion node
else if (compareResult > 0)
{
if (node.Left == null)
{
throw new Exception("Item do not exist");
}
delete(node.Left, value);
}
else
{
//node is a leaf node
if (node.IsLeaf)
{
//if node is root
if (node.Parent == null)
{
Root = null;
}
//assign nodes parent.left/right to null
else if (node.Parent.Left == node)
{
node.Parent.Left = null;
}
else
{
node.Parent.Right = null;
}
baseCase = true;
}
else
{
//case one - right tree is null (move sub tree up)
if (node.Left != null && node.Right == null)
{
//root
if (node.Parent == null)
{
Root.Left.Parent = null;
Root = Root.Left;
}
else
{
//node is left child of parent
if (node.Parent.Left == node)
{
node.Parent.Left = node.Left;
}
//node is right child of parent
else
{
node.Parent.Right = node.Left;
}
node.Left.Parent = node.Parent;
}
baseCase = true;
}
//case two - left tree is null (move sub tree up)
else if (node.Right != null && node.Left == null)
{
//root
if (node.Parent == null)
{
Root.Right.Parent = null;
Root = Root.Right;
}
else
{
//node is left child of parent
if (node.Parent.Left == node)
{
node.Parent.Left = node.Right;
}
//node is right child of parent
else
{
node.Parent.Right = node.Right;
}
node.Right.Parent = node.Parent;
}
baseCase = true;
}
//case three - two child trees
//replace the node value with maximum element of left subtree (left max node)
//and then delete the left max node
else
{
var maxLeftNode = findMax(node.Left);
node.Value = maxLeftNode.Value;
if (nodeLookUp != null)
{
nodeLookUp[node.Value] = node;
}
//delete left max node
delete(node.Left, maxLeftNode.Value);
}
}
}
if (baseCase)
{
UpdateHeight(node.Parent);
balance(node.Parent);
}
else
{
UpdateHeight(node);
balance(node);
}
}
