AVL TREE
#include<stdio.h>
#include<conio.h>

typedef enum { FALSE ,TRUE } bool;
struct node
{
int info;
int balance;
struct node *lchild;
struct node *rchild;
};

struct node *insert (int , struct node *, int *);
struct node* search(struct node *,int);

main()
{
bool ht_inc;
int info ;
int choice;                    
clrscr();
struct node *root = (struct node *)malloc(sizeof(struct node));
root = NULL;
while(1)
{
printf("1.Insert\n");
printf("2.Display\n");
printf("3.Quit\n");
printf("Enter your choice : ");
scanf("%d",&choice);
switch(choice)
{
case 1:
printf("Enter the value to be inserted : ");
scanf("%d", &info);
if( search(root,info) == NULL )
root = insert(info, root, &ht_inc);
else
printf("Duplicate value ignored\n");
break;
case 2:
if(root==NULL)
{
printf("Tree is empty\n");
continue;
}
printf("Tree is :\n");
display(root, 1);
printf("\n\n");
printf("\n");
break;
case 3:
exit(1);
default:
printf("Wrong choice\n");
}/*End of switch*/
}/*End of while*/
}/*End of main()*/

struct node* search(struct node *ptr,int info)
{
if(ptr!=NULL)
if(info < ptr->info)
ptr=search(ptr->lchild,info);
else if( info > ptr->info)
ptr=search(ptr->rchild,info);
return(ptr);
}/*End of search()*/

struct node *insert (int info, struct node *pptr, int *ht_inc)
{
struct node *aptr;
struct node *bptr;
if(pptr==NULL)
{
pptr = (struct node *) malloc(sizeof(struct node));
pptr->info = info;
pptr->lchild = NULL;
pptr->rchild = NULL;
pptr->balance = 0;
*ht_inc = TRUE;
return (pptr);
}
if(info < pptr->info)
{
pptr->lchild = insert(info, pptr->lchild, ht_inc);
if(*ht_inc==TRUE)
{
switch(pptr->balance)
{
case -1: /* Right heavy */
pptr->balance = 0;
*ht_inc = FALSE;
break;
case 0: /* Balanced */
pptr->balance = 1;
break;
case 1: /* Left heavy */
aptr = pptr->lchild;
if(aptr->balance == 1)
{
printf("Left to Left Rotation\n");
pptr->lchild= aptr->rchild;
aptr->rchild = pptr;
pptr->balance = 0;
aptr->balance=0;
pptr = aptr;
}
else
{
printf("Left to right rotation\n");
bptr = aptr->rchild;
aptr->rchild = bptr->lchild;
bptr->lchild = aptr;
pptr->lchild = bptr->rchild;
bptr->rchild = pptr;
if(bptr->balance == 1 )
pptr->balance = -1;
else
pptr->balance = 0;
if(bptr->balance == -1)
aptr->balance = 1;
else
aptr->balance = 0;
bptr->balance=0;
pptr=bptr;
}
*ht_inc = FALSE;
}/*End of switch */
}/*End of if */
}/*End of if*/
if(info > pptr->info)
{
pptr->rchild = insert(info, pptr->rchild, ht_inc);
if(*ht_inc==TRUE)
{
switch(pptr->balance)
{
case 1: /* Left heavy */
pptr->balance = 0;
*ht_inc = FALSE;
break;
case 0: /* Balanced */
pptr->balance = -1;
break;
case -1: /* Right heavy */
aptr = pptr->rchild;
if(aptr->balance == -1)
{
printf("Right to Right Rotation\n");
pptr->rchild= aptr->lchild;
aptr->lchild = pptr;
pptr->balance = 0;
aptr->balance=0;
pptr = aptr;
}
else
{
printf("Right to Left Rotation\n");
bptr = aptr->lchild;
aptr->lchild = bptr->rchild;
bptr->rchild = aptr;
pptr->rchild = bptr->lchild;
bptr->lchild = pptr;

if(bptr->balance == -1)
pptr->balance = 1;
else
pptr->balance = 0;
if(bptr->balance == 1)
aptr->balance = -1;
else
aptr->balance = 0;
bptr->balance=0;
pptr = bptr;
}/*End of else*/
*ht_inc = FALSE;
}/*End of switch */
}/*End of if*/
}/*End of if*/

return(pptr);
}/*End of insert()*/

display(struct node *ptr,int level)
{
int i;
if ( ptr!=NULL )
{
display(ptr->rchild, level+1);
printf("\n");
for (i = 0; i < level; i++)
printf(" ");
printf("%d", ptr->info);
display(ptr->lchild, level+1);
}/*End of if*/
}/*End of display()*/