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AVL Creation.cpp

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+/*
+
+Height of AVL Tree always log(n)
+Every AVL is a BST
+
+Single rotation -
+LL, RR
+
+Double rotation -
+LR, RL (single rotation is applied in double rotation)
+
+*/
+#include <bits/stdc++.h>
+using namespace std;
+
+class node {
+	public:
+		int data, height;  // height = balance factor
+		node *left, *right;
+};
+
+node* NewNode(int data) {
+	node *nn;
+	nn = new(node);
+	nn->left=NULL;
+	nn->right=NULL;
+	nn->height=1;
+	nn->data=data;
+	return nn;
+}
+
+int Height(node *root) {
+	if(root == NULL)
+	return 0;
+	return root->height;
+	}
+
+int max(int a, int b){
+	return a>b?a:b;
+}
+
+int GetBalance(node *root) {
+	if(root == NULL)
+	return 0;
+
+	return Height(root->left)-Height(root->right);
+}
+
+node *LeftRotation(node *y) {
+	node *x = y->left;
+	node *t2 = x->right;
+	x->right = y;
+	y->left = t2;
+
+//	update height
+	y->height = 1+max(Height(y->left),Height(y->right));
+	x->height = 1+max(Height(x->left),Height(x->right));
+	return x;
+}
+node *RightRotation(node *x) {
+	node *y = x->right;
+	node *t2 = y->left;
+	y->left = x;
+	x->right = t2;
+
+	x->height = 1+max(Height(x->left),Height(x->right));
+	y->height = 1+max(Height(y->left),Height(y->right));
+	return y;
+}
+
+node * Insert(node *root, int data) {
+	if(root==NULL)
+	return NewNode(data);
+	if(root->data > data)
+	Insert(root->left, data);
+	else if(root->data < data)
+	Insert(root->right, data);
+	else return root;
+
+	root->height = 1+max(Height(root->left),Height(root->right));
+
+	int balance = GetBalance(root);
+
+	if(balance > 1 && data < root->left->data) // LL Rotation
+	return LeftRotation(root);
+
+	if(balance < -1 && data > root->right->data) // RR Rotation
+	return RightRotation(root);
+
+	if(balance > 1 && data > root->left->data) { // LR Rotation First call right then left rotation
+		root->left = RightRotation(root->left);
+		return LeftRotation(root);
+	}
+
+	if(balance < -1 && data < root->right->data) { // RL Rotation First call left then right rotation
+		root->right = LeftRotation(root->right);
+		return RightRotation(root);
+	}
+
+	return root;
+
+}
+
+void Preorder(node *root) {
+	if(root==NULL)
+	return;
+	cout<<root->data<<" ";
+	Preorder(root->left);
+	Preorder(root->right);
+}
+int main()
+{
+	node * root=NULL;
+	root = Insert(root, 10);
+	root = Insert(root, 20);
+	root = Insert(root, 30);
+	Preorder(root);
+	return 0;
+}
+