# Avl tree node insertion in golang

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

``````package main
import "fmt"
// Go program
// AVL Tree insertion

// Avl Tree Node
type TreeNode struct {
data int
height int
left * TreeNode
right * TreeNode
}
func getTreeNode(data int) * TreeNode {
// Set node value of avl tree
return &TreeNode {data,1,nil,nil}
}
type AvlTree struct {
// Tree root node
root * TreeNode
}
func getAvlTree() * AvlTree {

// Set value of root
return  &AvlTree {nil}
}
// Get the height of given node
func(this AvlTree) getHeight(node * TreeNode) int {
if node == nil {
return 0
}
return node.height
}
// Get the max value of given two numbers
func(this AvlTree) maxHeight(a, b int) int {
if a > b {
return a
} else {
return b
}
}
// Perform the Right rotate operation
func(this *AvlTree) rightRotate(node * TreeNode) * TreeNode {
// Get left child node
var leftNode * TreeNode = node.left
// Get left node right subtree
var rightSubtree * TreeNode = 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
func(this *AvlTree) leftRotate(node * TreeNode) * TreeNode {
// Get right child node
var rightNode * TreeNode = node.right
// Get right node left subtree
var leftSubtree * TreeNode = 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
func(this AvlTree) getBalanceFactor(node * TreeNode) int {
if node == nil {
return 0
}
return this.getHeight(node.left) - this.getHeight(node.right)
}
// Recursively, add a node in AVL tree
// Duplicate keys (data) are not allowed
func(this *AvlTree) addNode(node * TreeNode, data int) * TreeNode {
if node == nil {
// Return a new node
return getTreeNode(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 int = 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
func(this AvlTree) preorder(node * TreeNode) {
if node != nil {
fmt.Print("  ", node.data)
this.preorder(node.left)
this.preorder(node.right)
}
}
// Print the tree in inorder form
func(this AvlTree) inorder(node * TreeNode) {
if node != nil {
this.inorder(node.left)
fmt.Print("  ", node.data)
this.inorder(node.right)
}
}
// Print the tree in postorder form
func(this AvlTree) postorder(node * TreeNode) {
if node != nil {
this.postorder(node.left)
this.postorder(node.right)
fmt.Print("  ", node.data)
}
}
func main() {
var tree * AvlTree = getAvlTree()
/*
Resultant  AVL Tree
-----------------
7
/  \
/    \
4      17
/ \     / \
2   5  13  19
/ \     /
-3   3   11
*/
fmt.Print("Resultant AVL Tree")
fmt.Print("\nPreorder  :")
tree.preorder(tree.root)
fmt.Print("\nInorder   :")
tree.inorder(tree.root)
fmt.Print("\nPostorder :")
tree.postorder(tree.root)
}``````

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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