import java.util.Scanner;
class Doublyll{
class Node{
int data;
Node next;
Node back;
Node(int d){
data=d;
}
}
Node head=null;
Node tail=null;
void insertnode(int data){
Node newnode=new Node(data);
if(head==null){
head=newnode;
tail=newnode;
head.back=null;
tail.next=null;
}
else{
tail.next=newnode;
newnode.back=tail;
tail=newnode;
tail.next=null;
}
}
public void display(){
Node current=head;
if(head==null)
System.out.println("No elements");
else{
while(current!=null){
System.out.print(current.data+" ");
current=current.next;
}
System.out.println();
}
}
public void frontdelete(){
try{
if(head==null)
System.out.println("No element to delete");
head=head.next;
if(head==null)
System.out.println("All elements are deleted");
}
catch(NullPointerException e){}
}
}
class Main{
public static void main(String[] args){
Doublyll d=new Doublyll();
int n,i,m,c;
Scanner s=new Scanner(System.in);
System.out.println("1.Insert 2.Display 3.Deletion from front");
while(4<10){
System.out.println("Enter choice:");
c=s.nextInt();
switch(c){
case 1:System.out.println("Enter no:");
m=s.nextInt();
d.insertnode(m);
break;
case 2:d.display();
break;
case 3:d.frontdelete();
break;
default:System.out.println("Invalid choice");
}}
}
}