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Node insertion in AVL Tree

Sid Skywalker answered on August 11, 2022 Popularity 9/10 Helpfulness 3/10

answer Node insertion in AVL Tree

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Node insertion in AVL Tree

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# Python code to insert a node in AVL tree
 
# Generic tree node class
class TreeNode(object):
    def __init__(self, val):
        self.val = val
        self.left = None
        self.right = None
        self.height = 1
 
# AVL tree class which supports the
# Insert operation
class AVL_Tree(object):
 
    # Recursive function to insert key in
    # subtree rooted with node and returns
    # new root of subtree.
    def insert(self, root, key):
     
        # Step 1 - Perform normal BST
        if not root:
            return TreeNode(key)
        elif key < root.val:
            root.left = self.insert(root.left, key)
        else:
            root.right = self.insert(root.right, key)
 
        # Step 2 - Update the height of the
        # ancestor node
        root.height = 1 + max(self.getHeight(root.left),
                           self.getHeight(root.right))
 
        # Step 3 - Get the balance factor
        balance = self.getBalance(root)
 
        # Step 4 - If the node is unbalanced,
        # then try out the 4 cases
        # Case 1 - Left Left
        if balance > 1 and key < root.left.val:
            return self.rightRotate(root)
 
        # Case 2 - Right Right
        if balance < -1 and key > root.right.val:
            return self.leftRotate(root)
 
        # Case 3 - Left Right
        if balance > 1 and key > root.left.val:
            root.left = self.leftRotate(root.left)
            return self.rightRotate(root)
 
        # Case 4 - Right Left
        if balance < -1 and key < root.right.val:
            root.right = self.rightRotate(root.right)
            return self.leftRotate(root)
 
        return root
 
    def leftRotate(self, z):
 
        y = z.right
        T2 = y.left
 
        # Perform rotation
        y.left = z
        z.right = T2
 
        # Update heights
        z.height = 1 + max(self.getHeight(z.left),
                         self.getHeight(z.right))
        y.height = 1 + max(self.getHeight(y.left),
                         self.getHeight(y.right))
 
        # Return the new root
        return y
 
    def rightRotate(self, z):
 
        y = z.left
        T3 = y.right
 
        # Perform rotation
        y.right = z
        z.left = T3
 
        # Update heights
        z.height = 1 + max(self.getHeight(z.left),
                        self.getHeight(z.right))
        y.height = 1 + max(self.getHeight(y.left),
                        self.getHeight(y.right))
 
        # Return the new root
        return y
 
    def getHeight(self, root):
        if not root:
            return 0
 
        return root.height
 
    def getBalance(self, root):
        if not root:
            return 0
 
        return self.getHeight(root.left) - self.getHeight(root.right)
 
    def preOrder(self, root):
 
        if not root:
            return
 
        print("{0} ".format(root.val), end="")
        self.preOrder(root.left)
        self.preOrder(root.right)
 
 
# Driver program to test above function
myTree = AVL_Tree()
root = None
 
root = myTree.insert(root, 10)
root = myTree.insert(root, 20)
root = myTree.insert(root, 30)
root = myTree.insert(root, 40)
root = myTree.insert(root, 50)
root = myTree.insert(root, 25)
 
"""The constructed AVL Tree would be
            30
           /  \
         20   40
        /  \     \
       10  25    50"""
 
# Preorder Traversal
print("Preorder traversal of the",
      "constructed AVL tree is")
myTree.preOrder(root)
print()
 
# This code is contributed by Ajitesh Pathak

Popularity 9/10 Helpfulness 3/10 Language python

Source: www.geeksforgeeks.org

Tags: avl-tree insertion python

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Contributed on Aug 11 2022

Sid Skywalker

0 Answers Avg Quality 2/10

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AVL tree insertion

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// C program to insert a node in AVL tree
#include<stdio.h>
#include<stdlib.h>
 
// An AVL tree node
struct Node
{
    int key;
    struct Node *left;
    struct Node *right;
    int height;
};
 
// A utility function to get the height of the tree
int height(struct 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. */
struct Node* newNode(int key)
{
    struct Node* node = (struct Node*)
                        malloc(sizeof(struct 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.
struct Node *rightRotate(struct Node *y)
{
    struct Node *x = y->left;
    struct 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.
struct Node *leftRotate(struct Node *x)
{
    struct Node *y = x->right;
    struct 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(struct 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.
struct Node* insert(struct 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(struct Node *root)
{
    if(root != NULL)
    {
        printf("%d ", root->key);
        preOrder(root->left);
        preOrder(root->right);
    }
}
 
/* Driver program to test above function*/
int main()
{
  struct 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
  */
 
  printf("Preorder traversal of the constructed AVL"
         " tree is \n");
  preOrder(root);
 
  return 0;
}

Popularity 9/10 Helpfulness 1/10 Language whatever

Source: www.geeksforgeeks.org

Tags: avl-tree avl-tre

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Contributed on Aug 25 2023

Ashamed Angelfish

0 Answers Avg Quality 2/10

Node insertion in AVL Tree

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