C Program to check if a Binary tree is AVL Tree or Not

By | May 10, 2017

Check Binary tree is AVL Tree or Not


Write a C Program to check if a Binary tree is AVL Tree or Not. Here’s simple Program to check if a Binary tree is AVL Tree or Not in C Programming Language.


AVL Tree


AVL tree is a self balanced binary search tree. That means, an AVL tree is also a binary search tree but it is a balanced tree. A binary tree is said to be balanced, if the difference between the heights of left and right subtrees of every node in the tree is either -1, 0 or +1.

In other words, a binary tree is said to be balanced if for every node, height of its children differ by at most one. In an AVL tree, every node maintains a extra information known as balance factor.

Balance factor of a node is the difference between the heights of left and right subtrees of that node. The balance factor of a node is calculated either height of left subtree – height of right subtree (OR) height of right subtree – height of left subtree.

  • Balance factor = heightOfLeftSubtree – heightOfRightSubtree

Also Read : : C Program to implement AVL Tree and its operations

Below is the source code for C Program to check if a Binary tree is AVL Tree or Not which is successfully compiled and run on Windows System to produce desired output as shown below :


SOURCE CODE : :


/*  C Program to check if a Binary tree is AVL Tree or Not  */

#include<stdio.h>
#include<stdlib.h>
#define MAX 50

struct node
{
	struct node *lchild;
	int info;
	struct node *rchild;
};

struct node *insert(struct node *ptr, int ikey);
int height(struct node *ptr);
int isAVL(struct node *ptr);
struct node *insert(struct node *ptr, int ikey );
int main( )
{
	struct node *root=NULL,*copy_root=NULL, *root1=NULL;
	root = insert(root, 6);
	root = insert(root, 3);
	root = insert(root, 8);
	root = insert(root, 7);
	root = insert(root, 1);
	root = insert(root, 4);
	root = insert(root, 9);
	root = insert(root, 10);
	root = insert(root, 11);
	if( isAVL(root) )
		printf("AVL\n");
	else
		printf("Not AVL\n");
}/*End of main( )*/

int isAVL(struct node *ptr)
{
	int h_l, h_r, diff;
	if(ptr == NULL)
		return 1;
	h_l = height(ptr->lchild);
	h_r = height(ptr->rchild);
	diff = h_l>h_r ? h_l-h_r : h_r-h_l;
	if( diff<=1 &&  isAVL(ptr->lchild) && isAVL(ptr->rchild) )
		return 1;
	return 0;
}

int height(struct node *ptr)
{
	int h_left, h_right;

	if (ptr == NULL) /*Base Case*/
		return 0;

	h_left =  height(ptr->lchild);
	h_right = height(ptr->rchild);

	if (h_left > h_right)
		return 1 + h_left;
	else
		return 1 + h_right;
}/*End of height()*/


struct node *insert(struct node *ptr, int ikey )
{
	if(ptr==NULL)
	{
		ptr = (struct node *) malloc(sizeof(struct node));
		ptr->info = ikey;
		ptr->lchild = NULL;
		ptr->rchild = NULL;
	}
	else if(ikey < ptr->info)	/*Insertion in left subtree*/
		ptr->lchild = insert(ptr->lchild, ikey);
	else if(ikey > ptr->info)	/*Insertion in right subtree */
		ptr->rchild = insert(ptr->rchild, ikey);
	else
		printf("Duplicate key\n");
	return(ptr);
}/*End of insert( )*/

OUTPUT : :


/* C Program to check if a Binary tree is AVL Tree or Not */

1.Insert Tree
2.Display Tree
3.Check AVL tree
4.Quit

Enter your choice : 1

Enter the key to be inserted : 6

1.Insert Tree
2.Display Tree
3.Check AVL tree
4.Quit

Enter your choice : 1

Enter the key to be inserted : 4

1.Insert Tree
2.Display Tree
3.Check AVL tree
4.Quit

Enter your choice : 1

Enter the key to be inserted : 5

1.Insert Tree
2.Display Tree
3.Check AVL tree
4.Quit

Enter your choice : 1

Enter the key to be inserted : 3

1.Insert Tree
2.Display Tree
3.Check AVL tree
4.Quit

Enter your choice : 1

Enter the key to be inserted : 7

1.Insert Tree
2.Display Tree
3.Check AVL tree
4.Quit

Enter your choice : 1

Enter the key to be inserted : 8

1.Insert Tree
2.Display Tree
3.Check AVL tree
4.Quit

Enter your choice : 2


        8
    7
6
        5
    4
        3

1.Insert Tree
2.Display Tree
3.Check AVL tree
4.Quit

Enter your choice : 3

The Given Binary Tree is AVL Tree.

1.Insert Tree
2.Display Tree
3.Check AVL tree
4.Quit

Enter your choice : 1

Enter the key to be inserted : 2

1.Insert Tree
2.Display Tree
3.Check AVL tree
4.Quit

Enter your choice : 1

Enter the key to be inserted : 1

1.Insert Tree
2.Display Tree
3.Check AVL tree
4.Quit

Enter your choice : 2


        8
    7
6
        5
    4
        3
            2
                1

1.Insert Tree
2.Display Tree
3.Check AVL tree
4.Quit

Enter your choice : 3

The Given Tree is Not AVL Tree

1.Insert Tree
2.Display Tree
3.Check AVL tree
4.Quit

Enter your choice : 4

Process returned 1

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