DoubleLinkList.java

package com.interview.linklist;

public class DoubleLinkList {

    public Node addNode(Node head,int data){
        if(head == null){
            head = Node.newNode(data);
            return head;
        }
        Node newNode = Node.newNode(data);
        Node current = head;
        while(current.next != null){
            current = current.next;
        }
        current.next = newNode;
        newNode.before = current;
        return head;
    }
    
    public Node addAtFront(Node head, int data){
        Node newNode = Node.newNode(data);
        if(head == null){
            return newNode;
        }
        newNode.next = head;
        head.before = newNode;
        return newNode;
    }
    
    public void print(Node head){
        while(head != null){
            System.out.print(head.data + " ");
            head = head.next;
        }
    }
    

    public void printFrontBack(Node head){
        Node prev = null;
        while(head != null){
            System.out.print(head.data + " ");
            prev = head;
            head = head.next;
        }
        System.out.println();
        while(prev != null){
            System.out.print(prev.data + " ");
            prev = prev.before;
        }
    }
    
    public Node find(Node head, int data){
        while(head != null){
            if(head.data == data){
                return head;
            }
            head = head.next;
        }
        return null;
    }
    
    public static void main(String args[]){
        DoubleLinkList dll = new DoubleLinkList();
        Node head = null;
        head = dll.addNode(head,1);
        head = dll.addNode(head,2);
        head = dll.addNode(head,3);
        head = dll.addNode(head,4);
        head = dll.addNode(head,5);
        dll.print(head);
    }
}