reverse-doubly-linked-list.js

'use strict';
/*
 Title: Reverse a doubly linked list
 Difficulty: Easy
 Score: 5
 Link: https://www.hackerrank.com/challenges/reverse-a-doubly-linked-list/problem
*/


function reverse(head) {
    while (head.next) {
        head = head.next
    }
    
    const newList = new DoublyLinkedList();

    while (head) {
        newList.insertNode(head.data);
        head = head.prev
    }
    return newList.head 
}

class DoublyLinkedListNode {
    constructor(nodeData) {
        this.data = nodeData;
        this.next = null;
        this.prev = null;
    }
};

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

    insertNode(nodeData) {
        let node = new DoublyLinkedListNode(nodeData);

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

        this.tail = node;
    }
};

module.exports =  {
    reverse, 
    DoublyLinkedList,
    DoublyLinkedListNode
}