avl tree implementation c++ code example

Example 1: avl tree implementation c++

// AVL tree implementation in C++

#include <iostream>
using namespace std;

class Node {
   public:
  int key;
  Node *left;
  Node *right;
  int height;
};

int max(int a, int b);

// Calculate height
int height(Node *N) {
  if (N == NULL)
    return 0;
  return N->height;
}

int max(int a, int b) {
  return (a > b) ? a : b;
}

// New node creation
Node *newNode(int key) {
  Node *node = new Node();
  node->key = key;
  node->left = NULL;
  node->right = NULL;
  node->height = 1;
  return (node);
}

// Rotate right
Node *rightRotate(Node *y) {
  Node *x = y->left;
  Node *T2 = x->right;
  x->right = y;
  y->left = T2;
  y->height = max(height(y->left),
          height(y->right)) +
        1;
  x->height = max(height(x->left),
          height(x->right)) +
        1;
  return x;
}

// Rotate left
Node *leftRotate(Node *x) {
  Node *y = x->right;
  Node *T2 = y->left;
  y->left = x;
  x->right = T2;
  x->height = max(height(x->left),
          height(x->right)) +
        1;
  y->height = max(height(y->left),
          height(y->right)) +
        1;
  return y;
}

// Get the balance factor of each node
int getBalanceFactor(Node *N) {
  if (N == NULL)
    return 0;
  return height(N->left) -
       height(N->right);
}

// Insert a node
Node *insertNode(Node *node, int key) {
  // Find the correct postion and insert the node
  if (node == NULL)
    return (newNode(key));
  if (key < node->key)
    node->left = insertNode(node->left, key);
  else if (key > node->key)
    node->right = insertNode(node->right, key);
  else
    return node;

  // Update the balance factor of each node and
  // balance the tree
  node->height = 1 + max(height(node->left),
               height(node->right));
  int balanceFactor = getBalanceFactor(node);
  if (balanceFactor > 1) {
    if (key < node->left->key) {
      return rightRotate(node);
    } else if (key > node->left->key) {
      node->left = leftRotate(node->left);
      return rightRotate(node);
    }
  }
  if (balanceFactor < -1) {
    if (key > node->right->key) {
      return leftRotate(node);
    } else if (key < node->right->key) {
      node->right = rightRotate(node->right);
      return leftRotate(node);
    }
  }
  return node;
}

// Node with minimum value
Node *nodeWithMimumValue(Node *node) {
  Node *current = node;
  while (current->left != NULL)
    current = current->left;
  return current;
}

// Delete a node
Node *deleteNode(Node *root, int key) {
  // Find the node and delete it
  if (root == NULL)
    return root;
  if (key < root->key)
    root->left = deleteNode(root->left, key);
  else if (key > root->key)
    root->right = deleteNode(root->right, key);
  else {
    if ((root->left == NULL) ||
      (root->right == NULL)) {
      Node *temp = root->left ? root->left : root->right;
      if (temp == NULL) {
        temp = root;
        root = NULL;
      } else
        *root = *temp;
      free(temp);
    } else {
      Node *temp = nodeWithMimumValue(root->right);
      root->key = temp->key;
      root->right = deleteNode(root->right,
                   temp->key);
    }
  }

  if (root == NULL)
    return root;

  // Update the balance factor of each node and
  // balance the tree
  root->height = 1 + max(height(root->left),
               height(root->right));
  int balanceFactor = getBalanceFactor(root);
  if (balanceFactor > 1) {
    if (getBalanceFactor(root->left) >= 0) {
      return rightRotate(root);
    } else {
      root->left = leftRotate(root->left);
      return rightRotate(root);
    }
  }
  if (balanceFactor < -1) {
    if (getBalanceFactor(root->right) <= 0) {
      return leftRotate(root);
    } else {
      root->right = rightRotate(root->right);
      return leftRotate(root);
    }
  }
  return root;
}

// Print the tree
void printTree(Node *root, string indent, bool last) {
  if (root != nullptr) {
    cout << indent;
    if (last) {
      cout << "R----";
      indent += "   ";
    } else {
      cout << "L----";
      indent += "|  ";
    }
    cout << root->key << endl;
    printTree(root->left, indent, false);
    printTree(root->right, indent, true);
  }
}

int main() {
  Node *root = NULL;
  root = insertNode(root, 33);
  root = insertNode(root, 13);
  root = insertNode(root, 53);
  root = insertNode(root, 9);
  root = insertNode(root, 21);
  root = insertNode(root, 61);
  root = insertNode(root, 8);
  root = insertNode(root, 11);
  printTree(root, "", true);
  root = deleteNode(root, 13);
  cout << "After deleting " << endl;
  printTree(root, "", true);
}

Example 2: avl tree c implementation

#include <stdio.h>
#include "avltree.h"
/*
    remove all nodes of an AVL tree
*/
void dispose(node* t)
{
    if( t != NULL )
    {
        dispose( t->left );
        dispose( t->right );
        free( t );
    }
}
 
/*
    find a specific node's key in the tree
*/
node* find(int e, node* t )
{
    if( t == NULL )
        return NULL;
    if( e < t->data )
        return find( e, t->left );
    else if( e > t->data )
        return find( e, t->right );
    else
        return t;
}
 
/*
    find minimum node's key
*/
node* find_min( node* t )
{
    if( t == NULL )
        return NULL;
    else if( t->left == NULL )
        return t;
    else
        return find_min( t->left );
}
 
/*
    find maximum node's key
*/
node* find_max( node* t )
{
    if( t != NULL )
        while( t->right != NULL )
            t = t->right;
 
    return t;
}
 
/*
    get the height of a node
*/
static int height( node* n )
{
    if( n == NULL )
        return -1;
    else
        return n->height;
}
 
/*
    get maximum value of two integers
*/
static int max( int l, int r)
{
    return l > r ? l: r;
}
 
/*
    perform a rotation between a k2 node and its left child
 
    note: call single_rotate_with_left only if k2 node has a left child
*/
 
static node* single_rotate_with_left( node* k2 )
{
    node* k1 = NULL;
 
    k1 = k2->left;
    k2->left = k1->right;
    k1->right = k2;
 
    k2->height = max( height( k2->left ), height( k2->right ) ) + 1;
    k1->height = max( height( k1->left ), k2->height ) + 1;
    return k1; /* new root */
}
 
/*
    perform a rotation between a node (k1) and its right child
 
    note: call single_rotate_with_right only if
    the k1 node has a right child
*/
 
static node* single_rotate_with_right( node* k1 )
{
    node* k2;
 
    k2 = k1->right;
    k1->right = k2->left;
    k2->left = k1;
 
    k1->height = max( height( k1->left ), height( k1->right ) ) + 1;
    k2->height = max( height( k2->right ), k1->height ) + 1;
 
    return k2;  /* New root */
}
 
/*
 
    perform the left-right double rotation,
 
    note: call double_rotate_with_left only if k3 node has
    a left child and k3's left child has a right child
*/
 
static node* double_rotate_with_left( node* k3 )
{
    /* Rotate between k1 and k2 */
    k3->left = single_rotate_with_right( k3->left );
 
    /* Rotate between K3 and k2 */
    return single_rotate_with_left( k3 );
}
 
/*
    perform the right-left double rotation
 
   notes: call double_rotate_with_right only if k1 has a
   right child and k1's right child has a left child
*/
 
 
 
static node* double_rotate_with_right( node* k1 )
{
    /* rotate between K3 and k2 */
    k1->right = single_rotate_with_left( k1->right );
 
    /* rotate between k1 and k2 */
    return single_rotate_with_right( k1 );
}
 
/*
    insert a new node into the tree
*/
node* insert(int e, node* t )
{
    if( t == NULL )
    {
        /* Create and return a one-node tree */
        t = (node*)malloc(sizeof(node));
        if( t == NULL )
        {
            fprintf (stderr, "Out of memory!!! (insert)\n");
            exit(1);
        }
        else
        {
            t->data = e;
            t->height = 0;
            t->left = t->right = NULL;
        }
    }
    else if( e < t->data )
    {
        t->left = insert( e, t->left );
        if( height( t->left ) - height( t->right ) == 2 )
            if( e < t->left->data )
                t = single_rotate_with_left( t );
            else
                t = double_rotate_with_left( t );
    }
    else if( e > t->data )
    {
        t->right = insert( e, t->right );
        if( height( t->right ) - height( t->left ) == 2 )
            if( e > t->right->data )
                t = single_rotate_with_right( t );
            else
                t = double_rotate_with_right( t );
    }
    /* Else X is in the tree already; we'll do nothing */
 
    t->height = max( height( t->left ), height( t->right ) ) + 1;
    return t;
}
 
/*
    remove a node in the tree
*/
node* delete( int e, node* t )
{
    printf( "Sorry; Delete is unimplemented; %d remains\n", e );
    return t;
}
 
/*
    data data of a node
*/
int get(node* n)
{
    return n->data;
}
 
/*
    Recursively display AVL tree or subtree
*/
void display_avl(node* t)
{
    if (t == NULL)
        return;
    printf("%d",t->data);
 
    if(t->left != NULL)
        printf("(L:%d)",t->left->data);
    if(t->right != NULL)
        printf("(R:%d)",t->right->data);
    printf("\n");
 
    display_avl(t->left);
    display_avl(t->right);
}