# How Many Types of Queues Are There in Data Structure?

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Angela Bailey

In data structure, a queue is an abstract data type that follows the First-In-First-Out (FIFO) principle. It is commonly used in computer science to efficiently manage and process data. There are several types of queues that are used in different scenarios based on their specific characteristics and requirements.

## 1. Simple Queue

A simple queue, also known as a linear queue, is the most basic type of queue. It follows a simple rule where elements are inserted at the rear and removed from the front.

The first element inserted is the first one to be removed. This type of queue has a fixed size and can store a limited number of elements.

## 2. Circular Queue

A circular queue, also known as a ring buffer, overcomes the limitation of a simple queue by using a circular array as its underlying data structure. When the rear pointer reaches the end of the array, it wraps around to the beginning, making it a circular structure. This allows for efficient memory utilization and enables continuous insertion and deletion operations.

## 3. Priority Queue

A priority queue assigns a priority value to each element in the queue. The element with the highest priority value is always at the front and will be processed first when dequeued. This type of queue is useful when different elements have different levels of importance or urgency.

## 4. Double-ended Queue

A double-ended queue, also known as a deque, allows insertion and removal of elements from both ends – front and rear. This makes it more flexible than other types of queues as it supports both FIFO and LIFO (Last-In-First-Out) operations simultaneously.

## 5. Circular Double-ended Queue

The circular double-ended queue combines features of both circular queues and double-ended queues. It allows elements to be inserted and removed from both ends of the queue, and when the rear or front pointer reaches the end of the array, it wraps around to the beginning, creating a circular structure.

## 6. Priority Double-ended Queue

The priority double-ended queue is a combination of a priority queue and a double-ended queue. It allows elements to be inserted and removed from both ends while maintaining the order based on their priority values. The element with the highest priority will always be at the front.

• Simple Queue: Follows FIFO order and has a fixed size.
• Circular Queue: Circular structure with efficient memory utilization.
• Priority Queue: Elements have assigned priorities for processing order.
• Double-ended Queue: Allows insertion/removal from both ends (FIFO & LIFO).
• Circular Double-ended Queue: Combination of circular and double-ended queues.
• Priority Double-ended Queue: Combination of priority and double-ended queues.

In conclusion, these are some of the commonly used types of queues in data structures. Understanding their characteristics and purposes can help in choosing the most suitable queue for specific applications or algorithms.

### Suggested Reading:

• Data Structures: Queues Explained
• Difference Between Stack and Queue

I hope this article provided you with valuable insights into different types of queues in data structures!

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