construct avl tree from the following set of elements

// C++ program to insert a node in AVL tree  
#include<bits/stdc++.h> 
using namespace std; 
  
// An AVL tree node  
class Node  
{  
    public: 
    int key;  
    Node *left;  
    Node *right;  
    int height;  
};  
  
// A utility function to get maximum 
// of two integers  
int max(int a, int b);  
  
// A utility function to get the  
// height of the tree  
int height(Node *N)  
{  
    if (N == NULL)  
        return 0;  
    return N->height;  
}  
  
// A utility function to get maximum 
// of two integers  
int max(int a, int b)  
{  
    return (a > b)? a : b;  
}  
  
/* Helper function that allocates a  
   new node with the given key and  
   NULL left and right pointers. */
Node* newNode(int key)  
{  
    Node* node = new Node(); 
    node->key = key;  
    node->left = NULL;  
    node->right = NULL;  
    node->height = 1; // new node is initially 
                      // added at leaf  
    return(node);  
}  
  
// A utility function to right 
// rotate subtree rooted with y  
// See the diagram given above.  
Node *rightRotate(Node *y)  
{  
    Node *x = y->left;  
    Node *T2 = x->right;  
  
    // Perform rotation  
    x->right = y;  
    y->left = T2;  
  
    // Update heights  
    y->height = max(height(y->left), 
                    height(y->right)) + 1;  
    x->height = max(height(x->left), 
                    height(x->right)) + 1;  
  
    // Return new root  
    return x;  
}  
  
// A utility function to left  
// rotate subtree rooted with x  
// See the diagram given above.  
Node *leftRotate(Node *x)  
{  
    Node *y = x->right;  
    Node *T2 = y->left;  
  
    // Perform rotation  
    y->left = x;  
    x->right = T2;  
  
    // Update heights  
    x->height = max(height(x->left),     
                    height(x->right)) + 1;  
    y->height = max(height(y->left),  
                    height(y->right)) + 1;  
  
    // Return new root  
    return y;  
}  
  
// Get Balance factor of node N  
int getBalance(Node *N)  
{  
    if (N == NULL)  
        return 0;  
    return height(N->left) - height(N->right);  
}  
  
// Recursive function to insert a key 
// in the subtree rooted with node and 
// returns the new root of the subtree.  
Node* insert(Node* node, int key)  
{  
    /* 1. Perform the normal BST insertion */
    if (node == NULL)  
        return(newNode(key));  
  
    if (key < node->key)  
        node->left = insert(node->left, key);  
    else if (key > node->key)  
        node->right = insert(node->right, key);  
    else // Equal keys are not allowed in BST  
        return node;  
  
    /* 2. Update height of this ancestor node */
    node->height = 1 + max(height(node->left),  
                        height(node->right));  
  
    /* 3. Get the balance factor of this ancestor  
        node to check whether this node became  
        unbalanced */
    int balance = getBalance(node);  
  
    // If this node becomes unbalanced, then  
    // there are 4 cases  
  
    // Left Left Case  
    if (balance > 1 && key < node->left->key)  
        return rightRotate(node);  
  
    // Right Right Case  
    if (balance < -1 && key > node->right->key)  
        return leftRotate(node);  
  
    // Left Right Case  
    if (balance > 1 && key > node->left->key)  
    {  
        node->left = leftRotate(node->left);  
        return rightRotate(node);  
    }  
  
    // Right Left Case  
    if (balance < -1 && key < node->right->key)  
    {  
        node->right = rightRotate(node->right);  
        return leftRotate(node);  
    }  
  
    /* return the (unchanged) node pointer */
    return node;  
}  
  
// A utility function to print preorder  
// traversal of the tree.  
// The function also prints height  
// of every node  
void preOrder(Node *root)  
{  
    if(root != NULL)  
    {  
        cout << root->key << " ";  
        preOrder(root->left);  
        preOrder(root->right);  
    }  
}  
  
// Driver Code 
int main()  
{  
    Node *root = NULL;  
      
    /* Constructing tree given in  
    the above figure */
    root = insert(root, 10);  
    root = insert(root, 20);  
    root = insert(root, 30);  
    root = insert(root, 40);  
    root = insert(root, 50);  
    root = insert(root, 25);  
      
    /* The constructed AVL Tree would be  
                30  
            / \  
            20 40  
            / \ \  
        10 25 50  
    */
    cout << "Preorder traversal of the "
            "constructed AVL tree is \n";  
    preOrder(root);  
      
    return 0;  
}  
  
// This code is contributed by 
// rathbhupendra