# What Is Queue and Its Types in Data Structure?

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Scott Campbell

A queue is a fundamental data structure in computer science that follows the First-In-First-Out (FIFO) principle. It is similar to a real-life queue, where the person who arrives first gets served first. In programming, a queue allows you to store and retrieve elements in a specific order.

## Types of Queues

### 1. Simple Queue

A simple queue is the most basic type of queue, where elements are inserted at the rear and removed from the front. It operates on a First-In-First-Out (FIFO) basis, just like waiting in line for a movie ticket.

### 2. Circular Queue

A circular queue is an extension of a simple queue, but with a fixed size.

When new elements are added and reach the end of the queue, they start filling up from the beginning again. This creates a circular structure and avoids wastage of space.

### 3. Priority Queue

In some scenarios, elements in a queue may have different priorities. A priority queue assigns each element a priority value and serves elements based on their relative priority rather than their arrival time.

• Max Priority Queue: In this type of priority queue, elements with higher priority values are served first.
• Min Priority Queue: Here, elements with lower priority values get served first.

### 4. Deque (Double Ended Queue)

A deque is more versatile compared to other types of queues as it allows insertion and deletion at both ends. Elements can be added or removed from either the front or rear end based on specific requirements.

## Common Operations on Queues

The following are the typical operations performed on queues:

• Enqueue: Add an element to the rear of the queue.
• Dequeue: Remove and retrieve the element from the front of the queue.
• isEmpty: Check if the queue is empty.
• isFull: Check if the queue is full (applicable for fixed-size queues).
• getFront: Retrieve the element at the front of the queue without removing it.
• getRear: Retrieve the element at the rear of the queue without removing it.

The implementation of these operations may vary depending on the type of queue being used. It’s important to choose an appropriate type based on your specific use case to optimize performance and memory usage.

## In Conclusion

A queue is a versatile data structure that finds applications in various domains, including operating systems, network protocols, and algorithms. Understanding different types of queues and their operations can help you design efficient and scalable solutions for your programming needs. Remember to choose a queue type that best suits your requirements and enjoy organizing your data in a structured manner!