No Code Data Structures

Definition: A collection of elements that are stored next to each other in a line. Elements can only be inserted at one side of the structure and only deleted from the other side. This can be referred to simply by the phrase "first in, first out".

Real Life Example: Imagine that you are at a playground. Your friends Tom, Bob, and Bill all go down a slide in that order, one after the other. Because Tom went down first, he will be the first person to exit the slide. After him will be Bob and the last to exit will be Bill because he was the last to enter.

Note: The first element in a queue (closest to being removed) is referred to as the "front". The last element in a queue (most recent insertion) is referred to as the "rear" or "back".

Basic Queue Operations:

Enqueuing (a.k.a offering) an element. An element is added to the queue at the rear.

Dequeuing (a.k.a polling) an element. The front-most element is removed from the queue.

Fun Fact: Have you created a Youtube playlist before? If so, you have used a queue! The first video added to a playlist is the first one played (first in first out) and the last video added is the last one played (last in last out).

Commonly Used In:

Messaging apps.
Scheduling routine tasks for power plants, factories, etc.
Implementing other data structures.
Social media apps.

Other Similar Data Structures:

Priority Queue: A queue that assigns an intentional priority value to each item upon insertion. When a dequeue occurs, the item with the lowest priority value is deleted rather than the front. If two items are tied for lowest priority value, the one closest to the front is deleted.

Circular Queue/Ring Buffer: A queue in which elements are organized in a circle rather than a line so that less memory is wasted at the expense of constant enqueues and dequeues.