#include<stdio.h>
#include<conio.h>
#include<alloc.h>
struct node
{
int no;
struct node *pre,*next;
};
struct node *start=NULL,*last=NULL;


void Append()
{

	struct node *n;
	n=(struct node*)malloc(sizeof(struct node));
	printf("\nEnter no");
	scanf("%d",&n->no);
	n->next=NULL;
	if(start==NULL)
	{
		start=last=n;
		start->pre=NULL;
		return;
	}
	last->next=n;
	n->pre=last;
	last=n;
}

void ftraverse()
{
	struct node *p=start;
	if(start==NULL)
	{
		printf("\n Empty Link List");
		return;
	}
	while(p!=NULL)
	{
		printf("    %d",p->no);
		p=p->next;
	}
}

void btraverse()
{
	struct node *p=last;
	if(last==NULL)
	{
		printf("\n Empty Link List");
		return;
	}
	while(p!=NULL)
	{
		printf("  %d",p->no);
	p=p->pre;
	}
}
void Search(struct node *p)
{
	int val;
	if(p==NULL)
	{
		printf("\n Empty Link List");
		return;
	}
	printf("\n Enter element to be SEARched ");
	scanf(" %d",&val);
	if(p==start)
	{
		while(p!=NULL)
		{
			if(val==p->no)
			{
				printf("\n FOUnd");
				return;
			}
			p=p->next;
		}
	}
	else
	{
		while(p!=NULL)
		{
			if(val==p->no)
			{
				printf("\n FOUNd");
				return;
			}
			p=p->pre;
		}

		}

	printf("\n NOT Found");
}


void Update(struct node *p)
{
	int val;
	if(p==NULL)
	{
		printf("\nEmpty LINK lIST");
		return;
	}
	printf("enter element to be UPDated");
	scanf("%d",&val);
	if(p==start)
	{
		while(p!=NULL)
		{
			if(val==p->no)
			{
				printf("Enter no ");
				scanf("%d",&p->no);
				printf("\nUpdated");
				return;
			}
			p=p->next;
		}
	}
	else

	 {
		 while(p!=NULL)
		 {
			 if(val==p->no)
			 {
				 printf("\n Enter new no");
				scanf("%d",&p->no);
				 printf("\nUPDated");
				 return;
			 }
			 p=p->next;
			 }
			}
		 printf("\n %d NOT Found",val);
		 }




 void main()
 {
 int ch;
 clrscr();
 do
 {
 printf("\n 1 Append");
 printf("\n 2 Forward TRAverse");
 printf("\n 3 BAckward TRAverse");
 printf("\n 4 Search from Start");
 printf("\n 5 Search from LAST");
 printf("\n 6 UPdate from start");
 printf("\n 7 Update from LAST");
 printf("\n 0 EXIT");
 printf("\n Enter your choice");
 scanf("%d",&ch);
 switch(ch)
 {
 case 1:Append();
	break;
 case 2:ftraverse();
	break;
 case 3:btraverse();
	break;
 case 4: Search(start);
	break;
 case 5: Search(last);
	break;
 case 6: Update(start);
	break;
 case 7: Update(last);
	  break;

 case 0:
	  break;

 default: printf("\n Invalid Choice");
 }
 }while(ch!=0);
 getch();
 }