JavaScript Exercises: Print a Doubly Linked lists in reverse order

JavaScript Data Structures: Exercise-9 with Solution

Write a JavaScript program to create a Doubly Linked lists of n nodes and display it in reverse order.

Sample Solution:

JavaScript Code:

class Node {
	constructor(value) {
		this.value = value;
		this.next = null;
		this.previous = null;
	}
}

class DoublyLinkedList {
	constructor(value) {
		this.head = {
			value: value,
			next: null,
			previous: null
		};
		this.length = 0;
		this.tail = this.head;
	}

  add(newNode) {
    if (this.head === null) {
    this.head = newNode;
    this.tail = newNode;
    } 
    else
    {
    newNode.previous = this.tail;
    this.tail.next = newNode;
    this.tail = newNode;
  }

  this.length++;
   }
  
 reverse() {
    let current = this.head;
    let temp = null;
    while (current != null) {
        temp = current.previous;
        current.previous = current.next;
        current.next = temp;
        current = current.previous;
    }
    if (temp != null) {
        this.head = temp.previous;
    }
    return this.head;
}

  
 printList() {
		let current = this.head;
		let result = [];
		while (current !== null) {
			result.push(current.value);
			current = current.next;
		}
		console.log(result.join(' '));
		return this;
	}
}

let numList = new DoublyLinkedList();
numList.add(new Node(2));
numList.add(new Node(3));
numList.add(new Node(4));
numList.add(new Node(5));
numList.add(new Node(6));
numList.add(new Node(7));
console.log("Original Doubly Linked Lists:")
numList.printList();
console.log("Reverse Linked list:")
numList.reverse();
numList.printList();

Sample Output:

Original Doubly Linked Lists:
 2 3 4 5 6 7
Reverse Linked list:
7 6 5 4 3 2 

Flowchart:

Live Demo:

See the Pen javascript-doubly-linked-list-exercise-9 by w3resource (@w3resource) on CodePen.

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