Advantages of Circular Queue Over Linear Queue

Introduction

Hello Ninja! As you progress through the process of learning Data Structures, you must get curious about what are the advantages of using them. Each data structure has its advantages and disadvantages, and each is used in specific places.

In this article, we'll see the advantages of circular queues over linear queues.

Let's start by recalling what queues are.

Queue

A queue is one of the linear data structures having two ends i.e. the front end and the rear end.

The operations in a queue are carried out in First In, First Out (FIFO) order. This means, we can only add items to the rear end of the queue and delete items from its front end. A queue is a sequential collection of elements. Here, we cannot randomly access the elements. We can only access the elements that are pointed either by front or rear.

The operations are carried out on the element first pushed into the queue.

Just like stacks, you can implement queues with the help of arrays. Commonly used variables in the implementation of queues are:

Front: It points to the first element kept in the array representing the queue.
Rear: It points to the last element kept in the array representing the queue.

To learn more about queues, refer to this article.
Now, let's discuss the linear or simple queues in greater detail.

Linear Queue

A linear queue is commonly known as a "queue." A linear queue is an abstract linear data type with a predefined capacity.
It follows the "First in, First Out" (FIFO) principle; that is, the element that comes first will be removed first, just as in an actual queue you would see at a supermarket. It is open from both ends; one is for inserting, and the other is for removing the data. There are two main functions in a linear queue: enqueue and dequeue. Enqueue helps insert the data from one end. The dequeue operation helps remove the data from the other end of the queue.

Now, let us learn about circular queues.

Circular Queue

A circular queue is quite similar to a linear queue. The only thing that differentiates it from a linear queue is that the rear and front ends are connected in this queue. There is no end to this queue. This specialty gives rise to a lot of benefits.

The operations in a circular queue are as follows.

When enqueue is performed on a queue/circular queue, an element is added to the index where the rear end is pointing.
When a dequeue is performed, an element is removed from the index where the front is pointing.

Now we know about linear queues and circular queues. Let's look at a comparison between both of them.

Comparison Between Linear and Circular Queues

In a linear queue, the front starts pointing to the next element after the removal of an element. It means that the position where the front was pointing earlier remains empty.
For example, Consider a queue of size six. Imagine if we make one dequeue and multiple enqueue operations such that the rear end reaches the last element. Even if there is room in this queue, we cannot add more elements to it. Look at the following image to visualize this example.

In a circular queue, even if the position where the front was pointing becomes empty after removing an element, the space does not get wasted. This is because the rear can move circularly and start over from the first index once it reaches the end of the queue. This property of circular queues allows us to insert elements in vacant spaces that otherwise would get wasted.

For example, consider a circular queue of size 8. After a few enqueue and dequeue operations, the front points to index 3 and the rear points to index 4. We can add more elements to this queue if we want, as the rear can move to index 0.

In the above example image, four elements have been dequeued. The rear points to index four, and the front points to index three. If we want to add an element, say 37, we can add it to index 0, as the rear end moves circularly here. That is the main advantage of using a circular queue.

Let us now talk about the advantages of a circular queue over a linear queue.

Advantages of the Circular Queue Over Linear Queue

The advantages of a circular queue over a linear queue are listed below:

Flexible insertion and deletion: In a circular Queue, elements can be added till the Queue isn't full. But in the linear Queue, you can not add more elements once the rear end points to the last index.
Operation simplicity: In the linear queue, the element inserted first is the element to be deleted first. That is not the case with the circular queue because the front and rear are not fixed. That allows us to modify the order of insertion and deletion, which is extremely helpful.
Memory efficiency: Circular Queue is more efficient than a linear Queue because we can add elements until it's completely filled. Thus, no space is left over. While in a linear queue, the vacant spaces after dequeue operations can never be filled.

Let us now address some frequently asked questions.

Read about Application of Queue in Data Structure here.

Frequently Asked Questions

What is a queue?

A queue is a linear data structure with both ends open. It performs operations in First In, First Out (FIFO) order.

What are the types of queues?

There are four main types of queues. These are priority queues, double-ended queues, circular queues, and simple queues.

What are the uses of queues?

We use a queue in places where data has to be stored but only processed after some time. Some examples include – CPU scheduling, printer queue, phone calling system, etc.

What is a circular queue?

It is a variation of the linear queue where the front and rear ends are connected. It is a never-ending queue.

Why is a circular queue used?

Circular queues offer a clean and quick way of storing FIFO data with a maximum size. It provides efficient memory here. That's why it's convenient to use.

Conclusion

In this article, we discussed the differences and advantages between a circular queue and a linear queue. You can check the following articles related to queues.

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Happy Learning, Ninjas