# Avl tree node insertion in node js

Js program for Avl tree node insertion. Here problem description and explanation.

``````// Node JS program
// AVL Tree insertion

// Avl Tree Node
class TreeNode
{
constructor(data)
{
// Set node value of avl tree
this.data = data;
this.height = 1;
this.left = null;
this.right = null;
}
}
class AvlTree
{
constructor()
{
this.root = null;
}
// Get the height of given node
getHeight(node)
{
if (node == null)
{
return 0;
}
return node.height;
}
// Get the max value of given two numbers
maxHeight(a, b)
{
if (a > b)
{
return a;
}
else
{
return b;
}
}
// Perform the Right rotate operation
rightRotate(node)
{
// Get left child node
var leftNode = node.left;
// Get left node right subtree
var rightSubtree = leftNode.right;
// Update the left and right subtree
leftNode.right = node;
node.left = rightSubtree;
// Change the height of modified node
node.height = this.maxHeight(
this.getHeight(node.left),
this.getHeight(node.right)) + 1;
leftNode.height = this.maxHeight(
this.getHeight(leftNode.left),
this.getHeight(leftNode.right)) + 1;
return leftNode;
}
// Perform the Left Rotate operation
leftRotate(node)
{
// Get right child node
var rightNode = node.right;
// Get right node left subtree
var leftSubtree = rightNode.left;
// Update the left and right subtree
rightNode.left = node;
node.right = leftSubtree;
// Change the height of modified node
node.height = this.maxHeight(
this.getHeight(node.left),
this.getHeight(node.right)) + 1;
rightNode.height = this.maxHeight(
this.getHeight(rightNode.left),
this.getHeight(rightNode.right)) + 1;
return rightNode;
}
// Get the balance factor
getBalanceFactor(node)
{
if (node == null)
{
return 0;
}
return this.getHeight(node.left) -
this.getHeight(node.right);
}
// Recursively, add a node in AVL tree
// Duplicate keys (data) are not allowed
{
if (node == null)
{
// Return a new node
return new TreeNode(data);
}
if (data < node.data)
{
}
else if (data > node.data)
{
}
else
{
// When given key data already exists
return node;
}
// Change the height of current node
node.height = 1 + this.maxHeight(
this.getHeight(node.left),
this.getHeight(node.right));
// Get balance factor of a node
var factor = this.getBalanceFactor(node);
// LL Case
if (factor > 1 && data < node.left.data)
{
return this.rightRotate(node);
}
// RR Case
if (factor < -1 && data > node.right.data)
{
return this.leftRotate(node);
}
// LL Case
if (factor > 1 && data > node.left.data)
{
node.left = this.leftRotate(node.left);
return this.rightRotate(node);
}
// RR Case
if (factor < -1 && data < node.right.data)
{
node.right = this.rightRotate(node.right);
return this.leftRotate(node);
}
return node;
}
// Print the tree in preorder form
preorder(node)
{
if (node != null)
{
process.stdout.write("  " + node.data);
this.preorder(node.left);
this.preorder(node.right);
}
}
// Print the tree in inorder form
inorder(node)
{
if (node != null)
{
this.inorder(node.left);
process.stdout.write("  " + node.data);
this.inorder(node.right);
}
}
// Print the tree in postorder form
postorder(node)
{
if (node != null)
{
this.postorder(node.left);
this.postorder(node.right);
process.stdout.write("  " + node.data);
}
}
}

function main()
{
var tree = new AvlTree();
/*
Resultant  AVL Tree
-----------------
7
/  \
/    \
4      17
/ \     / \
2   5  13  19
/ \     /
-3   3   11
*/
process.stdout.write("Resultant AVL Tree");
process.stdout.write("\nPreorder  :");
tree.preorder(tree.root);
process.stdout.write("\nInorder   :");
tree.inorder(tree.root);
process.stdout.write("\nPostorder :");
tree.postorder(tree.root);
}
// Start program execution
main();``````

Output

``````Resultant AVL Tree
Preorder  :  7  4  2  -3  3  5  17  13  11  19
Inorder   :  -3  2  3  4  5  7  11  13  17  19
Postorder :  -3  3  2  5  4  11  13  19  17  7``````

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