AVL Tree

public class AVLTree {
  private class AVLNode {
    private int height;
    private int value;
    private AVLNode leftChild;
    private AVLNode rightChild;

    public AVLNode(int value) {
      this.value = value;
    }

    @Override
    public String toString() {
      return "Value=" + this.value;
    }
  }

  private AVLNode root;

  public void insert(int value) {
    root = insert(root, value);
  }

  private AVLNode insert(AVLNode root, int value) {
    if (root == null)
      return new AVLNode(value);

    if (value < root.value)
      root.leftChild = insert(root.leftChild, value);
    else
      root.rightChild = insert(root.rightChild, value);

    setHeight(root);

    return balance(root);
  }

  private AVLNode balance(AVLNode root) {
    if (isLeftHeavy(root)) {
      if (balanceFactor(root.leftChild) < 0)
        root.leftChild = rotateLeft(root.leftChild);
      return rotateRight(root);
    }
    else if (isRightHeavy(root)) {
      if (balanceFactor(root.rightChild) > 0)
        root.rightChild = rotateRight(root.rightChild);
      return rotateLeft(root);
    }
    return root;
  }

  private AVLNode rotateLeft(AVLNode root) {
    var newRoot = root.rightChild;

    root.rightChild = newRoot.leftChild;
    newRoot.leftChild = root;

    setHeight(root);
    setHeight(newRoot);

    return newRoot;
  }

  private AVLNode rotateRight(AVLNode root) {
    var newRoot = root.leftChild;

    root.leftChild = newRoot.rightChild;
    newRoot.rightChild = root;

    setHeight(root);
    setHeight(newRoot);

    return newRoot;
  }

  private void setHeight(AVLNode node) {
    node.height = Math.max(
            height(node.leftChild),
            height(node.rightChild)) + 1;
  }

  private boolean isLeftHeavy(AVLNode node) {
    return balanceFactor(node) > 1;
  }

  private boolean isRightHeavy(AVLNode node) {
    return balanceFactor(node) < -1;
  }

  private int balanceFactor(AVLNode node) {
    return (node == null) ? 0 : height(node.leftChild) - height(node.rightChild);
  }

  private int height(AVLNode node) {
    return (node == null) ? -1 : node.height;
  }
}

Avl tree c++

#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);
}
Code language: C++ (cpp)

Source: learnc.net

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