What Is Queue and Its Application in Data Structure?


Scott Campbell

A queue is a fundamental data structure in computer science that follows the First-In-First-Out (FIFO) principle. It is a collection of elements that supports two main operations: enqueue and dequeue.

Enqueue refers to the process of adding an element to the end of the queue, while dequeue removes and returns the element at the front of the queue. This behavior is similar to people standing in a line or a queue, where the first person who enters is also the first person to leave.

Applications of Queue Data Structure:

1. Simulation

Queues are extensively used in simulations to model real-life scenarios such as traffic, customer service, or process scheduling. For example, in a traffic simulation, vehicles arriving at an intersection can be represented as enqueue operations, while their departure would be modeled using dequeue operations.

2. Print Spooler

A print spooler utilizes a queue to manage multiple print requests from different users.

The spooler enqueues print jobs as they arrive and dequeues them one by one for printing. This ensures that print requests are processed in the order they were submitted.

3. Task Scheduling

Operating systems often use queues for task scheduling purposes. Each task or process has an associated priority value, and higher-priority tasks are dequeued and executed before lower-priority ones.

4. Breadth-First Search (BFS)

BFS is a graph traversal algorithm that explores all vertices of a graph level by level.

It uses a queue to keep track of which vertices need to be visited next. Starting with the source vertex, we enqueue its adjacent vertices and continue this process until all vertices have been visited.

The anatomy of Queue:

A queue can be implemented using arrays or linked lists. In both cases, two pointers are used: front and rear. The front pointer keeps track of the first element in the queue, while the rear pointer points to the last element.


  • Enqueue: Adds an element to the end of the queue.
  • Dequeue: Removes and returns the element at the front of the queue.
  • isEmpty: Checks if the queue is empty.
  • isFull: Checks if the queue is full (in case of a fixed-size implementation).
  • Front: Returns the element at the front of the queue without removing it.

Theory vs. Practice:

In theory, queues have a time complexity of O(1) for enqueue and dequeue operations. However, in practice, when using an array-based implementation, enqueue operations can have a time complexity of O(n) if resizing is required.

Linked list implementations can avoid resizing but have a slightly higher memory overhead per element compared to arrays.

It’s important to choose an implementation based on your specific use case and requirements.

In conclusion, queues are an essential data structure that finds applications in various domains such as simulations, task scheduling, print spooling, and graph algorithms. Understanding how queues work and their applications will help you design efficient algorithms and solve real-world problems effectively.

If you’d like to learn more about data structures and algorithms in HTML tutorials, check out our other articles for more insightful content!

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