Queue implemented via a doubly linked list - Node.js Data Structure

Node.js examples for Data Structure:Queue

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Description

Queue implemented via a doubly linked list

Demo Code

  
// Queue, implemented via a doubly linked list
//  Could also have been implemented also with an array, using push and unshift methods
//  methods: push, pop, size
  
function Node(data) {
  this.data = data;/*from   w w  w. ja  v a 2s .co m*/
}
  
function Queue(node) {
    this.head = node || null;
    this.tail = node || null;
}
  
Queue.prototype.push = function(node) {
  // set the new node's prev to the Queue's tail
  node.prev = this.tail;
  node.next = null;
  
  // set the Queue's tail to the new node
  this.tail.next = node;
  this.tail = node;
};
  
Queue.prototype.pop = function() {
  var firstItem = this.head;
  this.head = firstItem.next;
  this.head.prev = null;
  
  return firstItem;
};
  
Queue.prototype.size = function() {
  // todo: we could probably move the head and tail at the same time for O(n/2)
  var head = this.head;
  var size = 1;
  
  while (head.next !== null) {
    head = head.next;
    size++;
  }
  
  return size;
};
  
Queue.prototype.print = function() {
  var current = this.head;
  
  while (current.next !== null) {
    console.log(current.data);
    current = current.next;
  }
  
  console.log(current.data);
};
  
var head = new Node("my first node");
var queue = new Queue(head);
var someNode = new Node("second node");
var thirdNode = new Node("third node");
  
  
console.log('-------------------- QUEUES --------------------');
console.log('---------- push ----------');
  
queue.push(someNode);
queue.push(thirdNode);
queue.push(new Node('fourth node'));
queue.push(new Node('fifth node'));
queue.print();
  
  
console.log('---------- pop ----------');
  
console.log('Popped item: ', queue.pop());
console.log('New Queue:');
queue.print();
  
  
console.log('---------- size ----------');
  
console.log(queue.size());

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