Dequeue data structure simplified

dumtochukwu — Tue, 27 Apr 2021 12:03:37 +0000

Hello friends, in today's article, I'd be writing about my understanding of dequeue data structure, which would be helpful to us in one way or the other.

Recently, I have been reading and practising Data structure and algorithm in javascript, and one of the data structure, I came across that got me into making more research on it is the dequeue data structure.

So now let's get to know what this structure is, Dequeue is a data structure that allows both insertion and deletion of an element from both ends of a list.

The diagram above shows us clearly what a dequeue structure looks like. Dequeue can also be seen as the combination of Queues (FIFO = first in first out) and Stack (LIFO = last in first out) operations. Stacks and Queues are one ended operations, unlike the dequeue which is a double-ended operation because of what it does.

In the Dequeue system, we have the rear (i.e the end of a list) and front (which is the beginning). Elements can either be added from the front or from the rear and also can be removed vice-versa.

Now I'd drop a code snippet to show you how the dequeue data structure can be implemented in Javascript,

function Deque() {
  this.addFront = addFront
  this.removeFront = removeFront
  this.addBack = addBack
  this.removeBack = removeBack
  this.arr = []
  this.size =size
}

 function size(){
    return this.arr.length // returns the length of the list
 }

 function addFront(el) {
   return this.arr.unshift(el) // Adds an element to the beginning of the list
 }

 function addBack(el){
   return this.arr.push(el) // Adds an element to the rear(end) of the list
 }

  function removeFront(el){
    return this.arr.shift(el) // Removes element from the beginning of the list
  }

  function removeBack(el){
    return this.arr.pop(el) // Removes element from the end of the list
  }

The above code snippet creates a dequeue constructor and also chains different methods which we'd use to execute our operations.

let test = new Deque();
test.addFront('apple');
test.addFront('melon');
test.addBack('ragna')
test.arr // ['ragna', 'apple', 'melon']
test.size() // 3
test.removeBack() // pops out 'ragna'
test.arr // ['apple', 'melon']

Now we know how this operation work using Javascript.
Let's try to implement a palindrome checker using the dequeue system

function palindrome(str){
   let myQueue = new Deque();

   for(let i = 0; i < str.length; i++){
      myQueue.addBack(str[i])
   }

   let isEqual = false;

   while(myQueue.size() > 1){

     let front = myQueue.removeFront();
     let back = myQueue.removeBack();
     if(front === back){
       isEqual = true;

     }
   }
return isEqual
 }

console.log(palindrome('racecar')) // true

And this is how we implement a palindrome checker using a dequeue data structure in javascript. I hope you were able to learn one or two from this article. Kindly leave a reply or a like if you learnt something new thanks 😉.

DEV Community: dumtochukwu

Dequeue data structure simplified