Reverse-Doubly-Linked-List.java

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;

public class Solution {

    static class DoublyLinkedListNode {
        public int data;
        public DoublyLinkedListNode next;
        public DoublyLinkedListNode prev;

        public DoublyLinkedListNode(int nodeData) {
            this.data = nodeData;
            this.next = null;
            this.prev = null;
        }
    }

    static class DoublyLinkedList {
        public DoublyLinkedListNode head;
        public DoublyLinkedListNode tail;

        public DoublyLinkedList() {
            this.head = null;
            this.tail = null;
        }

        public void insertNode(int nodeData) {
            DoublyLinkedListNode node = new DoublyLinkedListNode(nodeData);

            if (this.head == null) {
                this.head = node;
            } else {
                this.tail.next = node;
                node.prev = this.tail;
            }

            this.tail = node;
        }
    }

    public static void printDoublyLinkedList(DoublyLinkedListNode node, String sep, BufferedWriter bufferedWriter) throws IOException {
        while (node != null) {
            bufferedWriter.write(String.valueOf(node.data));

            node = node.next;

            if (node != null) {
                bufferedWriter.write(sep);
            }
        }
    }

    /*
     * Complete the 'reverse' function below.
     *
     * The function is expected to return an INTEGER_DOUBLY_LINKED_LIST.
     * The function accepts INTEGER_DOUBLY_LINKED_LIST llist as parameter.
     */

    /*
     * For your reference:
     *
     * DoublyLinkedListNode {
     *     int data;
     *     DoublyLinkedListNode next;
     *     DoublyLinkedListNode prev;
     * }
     *
     */

    public static DoublyLinkedListNode reverse(DoublyLinkedListNode llist) {
    // Write your code here
    DoublyLinkedListNode currNode = llist;
    DoublyLinkedListNode node = llist;
    if(llist == null)
    return null;
    else{
        while(currNode != null)
        {
            //Swap
            DoublyLinkedListNode prev = currNode.prev;
            currNode.prev = currNode.next;
            currNode.next = prev;
            //Update
            node = currNode;
            currNode = currNode.prev;
            // node = currNode.prev;
            // currNode.next = node;
            // node.next = 
        }
       // System.out.println(llist.prev.data);
        return node;
    }

    }



    private static final Scanner scanner = new Scanner(System.in);