//Following methods are helper method for treeBalancing method
//Should not be used anywhere else.
#region Tree Balancing Helper methods
/// <summary>
/// private helper method: Hook up the node with the tree after apply supplied rotation function rotation
/// </summary>
/// <param name="stack"> the stack used to retrace the node visited </param>
/// <param name="node"> the node currently in processing</param>
/// <param name="func"> the rotation function</param>
private void HookUp(Stack <AvlNode <T> > stack, AvlNode <T> node, Func <AvlNode <T>, AvlNode <T> > func)
{
if (stack.Count > 0)
{
if (stack.Peek().Left != null && stack.Peek().Left.Data.CompareTo(node.Data) == 0)
{
stack.Peek().Left = func(node);
return;
}
stack.Peek().Right = func(node);
return;
}
Root = func(node);
}
/// <summary>
/// private helper method: calculate the balancing factor of given node
/// </summary>
/// <param name="node"> node need to calculate balancing factor</param>
/// <returns></returns>
private int GetBalancingFactor(AvlNode <T> node)
{
//no child, balancing factor is 0
if (node.IsLeafNode())
{
return(0);
}
//has two child, balancing factor is height of left subtree - height of right subtree
if (!node.HasOneChild())
{
return(node.Left.Height - node.Right.Height);
}
//only one child, return that child's height
if (node.Left != null) //child on the left
{
return(node.Left.Height);
}
return(0 - node.Right.Height); //child on the right
}
/// <summary>
/// Insert new data into AVL Tree.
/// If data is actually inserted, method will return true.
/// If duplicate data is found, duplicate data will not be inserted and method will return false.
/// </summary>
/// <param name="data">The data intended to be insert into this AVL Tree.</param>
/// <returns></returns>
public override bool Insert(T data)
{
//handling an empty tree
if (Root == null)
{
Root = new AvlNode <T>(data)
{
Height = 1
};
TreeSize++;
return(true);
}
var res = true;
var current = Root;
// use stack keep record of traverse path
var stack = new Stack <AvlNode <T> >();
stack.Push(current);
while (true)
{
// Data to be inserted is smaller then current node, go left
if (data.CompareTo(current.Data) < 0)
{
if (current.Left != null)
{
current = current.Left;
stack.Push(current);
continue;
}
// if has no left child, insert new node here
current.Left = new AvlNode <T>(data);
stack.Push(current.Left);
break;
}
// Duplicate data is not allowed in BST, if found, stop insertion and return false;
if (data.CompareTo(current.Data) == 0)
{
res = false;
break;
}
// Data to be inserted is bigger then current node, go right
if (current.Right != null)
{
current = current.Right;
stack.Push(current);
continue;
}
// If has no right child, insert new node here
current.Right = new AvlNode <T>(data);
stack.Push(current.Right);
break;
}
if (res)
{
// if data inserted, increase tree size and balancing the tree
TreeSize++;
TreeBalancing(stack);
}
return(res);
}
/// <summary>
/// Constructor of AVLTree with root node's data specified
/// this constructor creates an AVLTree contains only root node which holds specified data
/// </summary>
/// <param name="data"> the actual data the root node should hold </param>
public AvlTree(T data)
{
Root = new AvlNode <T>(data);
TreeSize++;
}
