text: const { NotImplementedError } = require('../extensions/index.js');
  const { ListNode } = require('../extensions/list-node.js');
  
  /**
   * Implement the Queue with a given interface via linked list (use ListNode extension above).
   *
   * @example
   * const queue = new Queue();
   *
   * queue.enqueue(1); // adds the element to the queue
   * queue.enqueue(3); // adds the element to the queue
   * queue.dequeue(); // returns the top element from queue and deletes it, returns 1
   * queue.getUnderlyingList() // returns { value: 3, next: null }
   */
  module.exports = class Queue {
  
    constructor() {
      this.queue = {};
    }
    
    getUnderlyingList() {
      return this.queue;
    }
  
    enqueue(value) {
      if (Object.keys(this.queue).length == 0) {
        this.queue = new ListNode(value);
      } else {
        let queue = this.queue;
        while (queue.next) {
          queue = queue.next;
        }
        queue.next = new ListNode(value);
      }
    }
  
    dequeue() {
      const value = this.queue.value;
      this.queue.value = this.queue.next.value;
      this.queue.next = this.queue.next.next;
      return value;
    }
  
  }
  