The Queue Data Structure.

Megh Agarwal
Feb 27 · 5 min read
Photo by Adrien Delforge on Unsplash

The basics

A queue is a linear data structure that follows an order in which the elements can be accessed. It is very similar to stacks, but the only difference is that a queue is open on both ends. One end is used to add elements, and the other end is used to remove elements. The technical term for adding and removing elements is called Enqueue and Dequeue, respectively.

A simple illustration of the queue data structure.

The methods

A queue utilizes these five methods.

  1. dequeue() — Removes and returns the first item entered in the queue
  2. isEmpty() — Returns true or false based on if the queue is empty or not
  3. front() — Returns the front element of the queue
  4. print() — Returns all the elements of the queue

A detailed example

A short comic strip, giving a basic idea about the queue data structure.
An illustration showing the queue data structure from the comic strip above.
An illustration showing the enqueue() operation in the queue data structure.

The Big O Notation

According to the queue data structure theory, all operations' time complexity should be O(1). For those who do not know what this means, O(1) is the most efficient time complexity a data structure or an algorithm can have. O(1) tells that, even if the number of elements in the queue increase, the time taken for that operation to complete will be constant.

An illustration of the dequeue operation in a queue implemented using an array.

Application/Uses of the queue data structure

There are multiple use cases of a queue data structure. Something that involves first come, first serve might use queues. Some real-world applications include:

  1. Model physical queues, people waiting in a line for a supermarket checkout
  2. When sending data over the internet, various data packets wait in a queue to be sent.
  3. A server responding to requests. Usually, these requests are stored in queues. The first-come, first responded policy is followed in such cases.

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Megh Agarwal

Written by

Incoming freshman at the University of Toronto. Founder, developer, designer of Pustakdaan. Experienced web developer. Interested in research (AI, ML).

Nerd For Tech

NFT is an Educational Media House. Our mission is to bring the invaluable knowledge and experiences of experts from all over the world to the novice. To know more about us, visit https://www.nerdfortech.org/.