Double Linked List

Double Linked List

import java.util.*;
class Node{
    int info;
    Node next;
    Node prev;
}
public class DLinkedList
{



 
    static Node create(Node start,Node end){
            Node p;
            Scanner sc=new Scanner(System.in);
            System.out.println(" Enter the node info:");
            start.info=sc.nextInt();
           
            start.prev=start.next=null;
            System.out.println("Do u want to add new node Yes-1/No-0 \n");
            int option=sc.nextInt();
            while(option != 0 )
                   {
                    p=new Node();
                    System.out.println("Enter the node info");
                    p.info=sc.nextInt();
                    p.prev=p.next=null;
                    p.prev=end;
                    end.next=p;
                    end=p;
                    System.out.println("Do u want to add new node Yes-1/No-0 \n");
                    option=sc.nextInt();
                    }

            return end;



}




    static void display(Node start,Node end)
   {
            Node p=start;
            while(p!=null)
            {
                    System.out.println(p.info);
                    p=p.next;
            }
    }

/*insertion in Double linked list
Insertion in doubly linked list
There are three situation for inserting element in list.
1.Insertion at the front of list.
2.Insertion in the middle of the list.
3.Insertion at the end of the list.
*/

    static Node InsertBeg(Node start, Node end)
    {
            Scanner sc=new Scanner(System.in);
            Node p=new Node();
            System.out.println("Enter the node info");
            p.info=sc.nextInt();
           
            p.prev=null;
            p.next=start;
            start.prev=p;
            start=p;
            return start;
    }


    static Node InsertEnd(Node start, Node end)
    {
            Scanner sc=new Scanner(System.in);
            Node p=new Node();
            System.out.println("Enter the node info");
            p.info=sc.nextInt();
           
            p.next=null;
            p.prev=end;
            end.next=p;
            end=p;
            return end;
    }
    static Node InsertAny(Node start, Node end){
            Scanner sc=new Scanner(System.in);
            System.out.println("Enter the index/location where to insert:");
            int loc=sc.nextInt();
            int count=1;
            Node  p=start;
            while(( p!=null)&&(count<(loc-1))){
                     p= p.next;count++;
                    }
            if( p==null) System.out.println("Too high index");
            else{
            Node curr=new Node();
            System.out.println("Enter the node info");
            curr.info=sc.nextInt();
           
            curr.next=curr.prev=null;
            curr.next= p.next;
             p.next.prev=curr;
            curr.prev= p;
             p.next=curr;
            }
            return end;
    }

    static Node DeleteBeg(Node start,Node end)
    {
            start.next.prev=null;
            start=start.next;
            return start;
    }

    static Node DeleteEnd(Node start,Node end)
    {
            end.prev.next=null;
            end =end.prev;
            return end;
    }

    static Node DeleteAny(Node start,Node end)
            {
            Scanner sc=new Scanner(System.in);
            Node p=start;
            System.out.println("Enter the node info to delete");
            int item=sc.nextInt();
            while(p!=null && p.info!=item)
                    p=p.next;
            if(p==null) System.out.println("Node not found");
            else{
                    p.prev.next=p.next;
                    p.next.prev=p.prev;
            }
            return start;
    }


    static void Search(Node start)
    {
            Scanner sc=new Scanner(System.in);
            System.out.println("Enter the node info to search");
            int roll=sc.nextInt();
            while(start!=null && start.info!=roll){
                    if(start.info==roll) break;
                    else start=start.next;
                    }
            if(start==null) System.out.println("node not present");
            else System.out.println("node is present");
    }


    public static void main(String[] args) 
            {
            Scanner sc=new Scanner(System.in);
            Node start=new Node();
            Node end=start;
            while(true){
            System.out.println("*********************MENU(Doubly Linked List)***************************");
            System.out.println("0: Exit");
            System.out.println("1: Creation");
            System.out.println("2: Display");
            System.out.println("3: Insert at the begenning");
            System.out.println("4: Insert at the end");
            System.out.println("5: Insert at any location");
            System.out.println("6: Delete the first node");
            System.out.println("7: Delete the last node");
            System.out.println("8: Delete any node");
            System.out.println("9: Search a node");
            System.out.println("Enter your choice");
            int choice=sc.nextInt();
            switch(choice){
            case 0:    System.exit(0);
            case 1:
                    end=create(start,end);
                    break;
            case 2:
                    display(start,end);
                    break;
            case 3:
                    start=InsertBeg(start,end);
                    break;
            case 4:
                    end=InsertEnd(start,end);
                    break;
            case 5:
                    end=InsertAny(start,end);
                    break;
            case 6:
                    start=DeleteBeg(start,end);
                    break;
            case 7:
                    end=DeleteEnd(start,end);
                    break;
            case 8:
                    start=DeleteAny(start,end);
                    break;
            case 9:
                    Search(start);
                    break;
            default:
                    System.out.println("Wrong choice");
                    }
            }
    }
   
}

Doubly Linked List
In this type of liked list each node holds two-pointer field. Pointers exist between adjacent nodes in both directions.The list can be traversed either forward or backward.

NEXT holds the memory location of the Previous Node in the List.

PREV holds the memory location of the Next Node in the List.

DATA holds Data.

Some Points About Doubly Linked-List
1.Doubly Linked List are more convenient than Singly Linked List since we maintain links for bi-directional traversing
2.We can traverse in both directions and display the contents in the whole List.
3.In Doubly Linked List we can traverse from Head to Tail as well as Tail to Head.
4. Each Node contains two fields, called Links , that are references to the previous and to the Next Node in the sequence of Nodes.
5. The previous link of the first node and the next link of the last node points to NULL.