import java.util.Scanner;
public class Node
{
int info;
Node next,prev;
Node left,right;
}
public class QueueLL
{
Node start=new Node();
Node end=new Node();
Node curr=new Node();
int ch,num;
Object obj=new Object();
QueueLL()
{
start=null;
end=null;
num=0;
}
void Add(int val)
{
Node t=new Node();
t.info=val;
if(num++==0)
start=t;
else
t.next=end;
end=t;
}
void Del()
{
if(num==0)
System.out.println("Queue is Empty");
else
{
if(start==end)
{
start=null;
end=null;
num=0;
}
else
{
curr=end;
while(curr.next!=start)
curr=curr.next;
start=curr;
start.next=null;
}
}
}
void Display()
{
curr=end;
System.out.print("Back -> ");
while(curr!=null)
{
System.out.print(curr.info + " -> ");
curr=curr.next;
}
System.out.println("Front");
}
public static void main(String args[])
{
int ch,val;
QueueLL q=new QueueLL();
Scanner in = new Scanner(System.in);
while(true)
{
System.out.println("Enter your Choice");
System.out.println("-------------------------------------");
System.out.println("1 : Add\t2 : Del\t3 : Display\t4 : Exit");
ch=in.nextInt();
switch(ch)
{
case 1:
{
System.out.print("Enter a Number = ");
val=in.nextInt();
q.Add(val);
break;
}
case 2:
{
q.Del();
break;
}
case 3:
{
q.Display();
break;
}
case 4:
System.exit(0);
break;
default : continue;
}
}
}
}