Percy  Ebert

Percy Ebert

1603263455

How To Create A Linked List, Stack and Queue in JavaScript

The linked list, stack and Queue are some of the most common data structures in computer science. All three hold a collection of elements and can be traversed. In the linked list one pointer is used to keep track of the head and another keeps track of the next value. On the other hand a stack and queue keeps track of the top value, size and previous value in most cases.

Each implementation of these data structures may differ slightly. The linked list can be written as a circularly linked list, double linked list or singly linked list. Depending on the implementation a stack may, or may not, keep track of the previous value.

Some other common data structures include trees, tries & graphs, heaps, array lists and hash tables. For the sake of this blog article we’ll just discuss linked lists, queues and stacks using JavaScript

In this blog post we’ll discuss how to implement a stack, queue and linked list using JavaScript.

I encourage you before you begin to try to implement these data structures by yourself first. Check back here and see how you did.

Linked List

A linked list is a linear collection of data elements, called nodes, each pointing to the next node. This is done by the use of of a pointer. See the below example.

<img src=“/content/images/2017/02/LinkedList.jpg” style=“max-width:100%;height:auto” align=“left”"/>

The first node is known as the head node. It points to the first element. We can use the pointer to traverse the elements in the node. The last node points to null.

To implement this data structure we’ll use prototypal inheritance using JavaScript. Let’s begin by creating a simple constructor function with a head pointion to null.

function LinkedList(){  
  this.head = null;
}

Now we need to implement the rest. We’ll use prototype object to extend the LinkedList function.

LinkedList.prototype.push = function(val){
    var node = {
       value: val,
       next: null
    }
    if(!this.head){
      this.head = node;      
    }
    else{
      current = this.head;
      while(current.next){
        current = current.next;
      }
      current.next = node;
    }
  }

The code above implements the rest of the linked list. Each node object will have a value and a pointer to null. A check is made if the head is empty. If so it’s set to head. Else a new node is created and appended to the end of the list.

Let’s check if it works!

let ll = new LinkedList();
// add
ll.push(235);
ll.push(245);
ll.push(123);

ll.head;  //Object value: 235
ll.head.next; //Object value: 245
ll.head.next.next //object value: 123

First we use the new keyword to create a new instance. We can then use the push method to add values. As you can see each value is added to a new node. We can access these nodes by using next value.

Pretty simple right? We could use ES6 classes to do the same thing, we’ll look at that in another post.

#javascript #programming #web-development #developer

What is GEEK

Buddha Community

How To Create A Linked List, Stack and Queue in JavaScript
August  Larson

August Larson

1624320600

How To Create a Linked List in Python

Practice your Python skills by implementing a linked list

What Is a Linked List?

A linked list is a basic data structure. It is a collection of nodes that connects each node to the next node with a pointer.

Each node consists of two items:

  • Data (such as a number)
  • Pointer to the next node

Here is an illustration of a linked list

Diagram explaining linked lists

A linked list forms a chain of nodes. Each node holds data and points to the next node. Image by the author.

#programming #coding #python #how to create a linked list in python #create a linked list #linked list

Willie  Beier

Willie Beier

1595641189

How To Implement Your First Linked List Data Structure In JavaScript

In this article, we are going to cover the concept of linked lists, what linked lists are and how to implement one in your project. This article covers the basic way to implement a linked list in JavaScript.

In this article, i will assume that you already know or have a basic knowledge of javascript and general programming concepts like strings and arrays.

A linked list is just another data structure like arrays , stacks or queues. A linked list unlike an array contains nodes where each node has a data part which stores our data and a next part or a reference to the next node in the list.

The nodes are connected together through links. In a more simple term, a linked list is a collection of nodes which are connected to each other through links. These nodes have two parts. The first part stores our data while the second part stores the address or link to the next node in the list.

Consider the diagram below.

The first node in a list is usually called a head. The head links to the next node through the next link and it continues till the last node which is not pointing to any other node, so the next value of the last node becomes NULL.

Linked lists cannot be accessed randomly. I.e you cannot access data with it’s index (this can be manipulated but it’s not like we do with arrays). In linked lists, we refer to the memory location Address, not the index location.

Now that we have a better understanding of linked lists. Let’s go on and implement it using javascript.

The first thing we are going to do is to create a node constructor function or class. I will be using ES6 classes in the article.

class Node{

constructor(data, next = null){
this.data = data;
this.next = next;
}

#javascript-tips #programming #linked-lists #javascript #javascript-development

Hertha  Mayer

Hertha Mayer

1595334123

Authentication In MEAN Stack - A Quick Guide

I consider myself an active StackOverflow user, despite my activity tends to vary depending on my daily workload. I enjoy answering questions with angular tag and I always try to create some working example to prove correctness of my answers.

To create angular demo I usually use either plunker or stackblitz or even jsfiddle. I like all of them but when I run into some errors I want to have a little bit more usable tool to undestand what’s going on.

Many people who ask questions on stackoverflow don’t want to isolate the problem and prepare minimal reproduction so they usually post all code to their questions on SO. They also tend to be not accurate and make a lot of mistakes in template syntax. To not waste a lot of time investigating where the error comes from I tried to create a tool that will help me to quickly find what causes the problem.

Angular demo runner
Online angular editor for building demo.
ng-run.com
<>

Let me show what I mean…

Template parser errors#

There are template parser errors that can be easy catched by stackblitz

It gives me some information but I want the error to be highlighted

#mean stack #angular 6 passport authentication #authentication in mean stack #full stack authentication #mean stack example application #mean stack login and registration angular 8 #mean stack login and registration angular 9 #mean stack tutorial #mean stack tutorial 2019 #passport.js

Lia  Haley

Lia Haley

1605854137

JavaScript Algorithm: How to Reverse Linked List

When given a singly linked list how can we manage to reverse it? Like the following example, if the input linked list is 1->2->3->4->5->NULL, can we reverse it into the output as 5->4->3->2->1->NULL?

Image for post

Example Input

Image for post

Example Output

Each node of Linked list will have two attributes: value & next, and linked list will have head, tail and length attribute.

function ListNode(val, next) {
     this.val = (val===undefined ? 0 : val)
     this.next = (next===undefined ? null : next)
 }

https://gist.github.com/GAierken/6e15c82f5e3457fa2d16e29400e130aa

There are two approaches to reverse a singly linked list: iterative and recursive.

#javascript #recursion #singly-linked-list #reverse-linked-list #iteration

Editing a Singly Linked List

In the previous “Data Structures in JavaScript” discussion, we walked through the methodology used to construct a node class which represent each “link” in the “chain” that is a linked list. From there we discussed how to construct a singly linked list from a an array. Building on the previous discussion, we will now dive into editing that singly linked list. If you are not familiar with the code and terminology covered in the previous article it is recommended you review Building a Singly Linked List.

With a linked list there are three ways to edit the list: update a nodes data property, add a node to the list or delete a node from the list. In all these cases, we will want to access a specific place in the singly linked list. Depending on the situation, you might want to edit the nth node from the head of the list, the nth node from the end of the list, or a node of a particular data value. For this discussion, we will assume that we are interested in editing the nth Node from the head of the list. With this in mind, we can step through a singly linked list from the head to the nth a node using a simple for loop as shown in Figure 1.

Image for post

#javascript #singly-linked-list #linked-lists #data-structures #algorithms