As you can see in the above image, after a bit of enqueuing and dequeuing, the size of the queue has been reduced. Hence we can consume the entire space of the queue till it becomes full. When initializing the queue, we set the value of FRONT and REARto -1. The operations are the same as discussed before except that in this case, we have to perform them with respect to the linked list nodes. Queue operations work as follows: 1. Let’s implement the circular queue using C++. * Queue is used in BFS(Breadth First Search) algorithm. Next, we insert or enqueue three more elements in the circular queue. #1) Check if the circular queue is full: test ((rear == SIZE-1 && front == 0) || (rear == front-1)), where ‘SIZE’ is the size of the circular queue. A circular queue is a linear data structure that is used to store data items. The output of the above program is similar to the previous program. If queue is not empty then perform step 3. Circular Queue works by the process of circular increment i.e. A circular linked list has the following components – Data: Value stored in a node is called the data. Due to this arrangement, space doesn’t go wasted as it happens in a linear queue. Overview of Queue Applications of Queues Insertion and deletion in a Linear queue Implementation of Circular Queue Dequeue Priority Queue Consider a situation where you have to create an application with the following set of requirements: Application should serve the requests of multiple users. If it is true then set front=rear= -1 else check if (front==size-1), if it is true then set front=0 and return the element. This Tutorial on C++ Circular Queue Data Structure Explains What is Circular Queue, What are the Basic Operations along with Implementation & Applications: A circular queue is an extension of the basic queue that we have discussed earlier. Circular queues fix the major disadvantage of a normal queue wherein we cannot insert elements when the rear pointer is at the end of the queue even when we delete the elements and space is emptied. If Yes, then return Queue is full. This property of Queue makes it also useful in following kind of scenarios. The structure of the circular linked list is like a closed loop. The indexes 0 and 1 can only be used after the queue is reset when all the elements have been dequeued. #2) If it is empty then display the message “Queue is empty”. Memory Management: The unused memory locations in the case of ordinary queues can be utilized in circular queues. #2) If the circular queue is full then it displays a message as “Queue is full”. Queue is used when things don’t have to be processed immediately, but have to be processed in F irst I n F irst O ut order like Breadth First Search. The following diagram shows a circular queue. The output shows the circular queue after enqueue operation, dequeue and also after the second enqueue operation. 3. Watch Now. 3.2. It performs operations by following the FIFO (First In, First Out) approach and the last position in the queue is connected back to the first position to form a circle. In the circular queue, the element is always deleted from the front end. Next, we insert or enqueue element 11 in the circular queue as represented below. In circular queue it is necessary that: Before insertion, fullness of Queue must be checked (for overflow). Given below is the sequence for dequeue operation in a circular queue. Finding the si… Note that we make use of struct to represent each node. Applications of Queue Data Structure. We have explored the types along with implementations. The most common queue implementation is using arrays, but it can also be implemented using lists. Consider the following circular queue of 5 elements as shown below: When we insert the elements to make a queue full, the representation will be as shown below. If it is true then set rear=0 and insert element. © Parewa Labs Pvt. A circular queue is a linear data structure that is used to store data items. First, we add the elements and then dequeue or remove two elements. Shruti Rawal However, the check for full queue has a new additional case: The second case happens when REAR starts from 0 due to circular increment and when its value is just 1 less than FRONT, the queue is full. Below we have the implementation of a circular queue: 1. Two pointers called FRONT and REARare used to keep track of the first and last elements in the queue. #1) Check if the circular queue is Empty: check if (front==-1). Rear: Returns the rear position in the circular queue. 2. 2.2. The different types of queues are linear queue, circular queue, priority queue and deque. 3. dequeue: Check if the number of elements in the queue is zero: 3.1. The complexity of the enqueue and dequeue operations of a circular queue is O(1) for (array implementations). Let’s discuss some of the applications of the circular queue. Some of the basic operations of the circular queue are as follows: Front: Returns the front position in the circular queue. In the next section, we will learn about the basic operations of the circular queue. If Yes, then return Queue is empty. That is. O… 1) When a resource is shared among multiple consumers. Queue is a FIFO (first in first out) data structure. when we try to increment any variable and we reach the end of the queue, we start from the beginning of the queue by modulo division with the queue size. It is also known as “Ring buffer”. Python Basics Video Course now on Youtube! Here, the circular increment is performed by modulo division with the queue size. 4. Traffic system: In a computer-controlled traffic system, circular queues are used to switch on the traffic lights one by one repeatedly as per the time set. In a circular queue, elements are arranged in a circular fashion, so that space is not wasted at all. Let’s discuss the linked list implementation of a circular queue now. Circular queues are mostly useful for scheduling purposes and applications like traffic signal systems where the signals glow in turns. Circular Queue works by the process of circular increment i.e. 2. enqueue: Check if the number of elements is equal to maxSize - 1: 2.1. Initialize the queue, with size of the queue defined (maxSize), and head and tailpointers. Now we delete the two elements i.e. Next implementation is a Java program to demonstrate circular queue using the linked list. If No, then add the new data element to the location of tail pointer and increment the tailpointer. => Look For The Entire C++ Training Series Here. In our next tutorial, we will learn about the double-ended queues that are simply called “deque”. #3) Check if (front==rear). Ltd. All rights reserved. item 1 and item 3 from the queue as shown below. It is also known as boundary case problem. Given below is the linked list implementation of the circular queue in C++. Enqueue: Enqueue (value) is used to insert an element in the circular queue. i.e. We have also seen the major operations of the circular queue. Join our newsletter for the latest updates. Again let us insert element 13 in the circular queue. If queue is not full then, check if (rear == SIZE – 1 && front != 0). Data Structures Types of Queue and their implementations. We see that unlike linear queue, the elements are added at the end of the queue. The queue will look as shown below. If No, then increment the headpointer. Above shown is the output of circular queue operations. when we try to increment the pointer and we reach the end of the queue, we start from the beginning of the queue. The drawback of circular queue is, difficult to distinguished the full and empty cases. The above image shows a circular data structure of size 10. In the circular queue, when the queue is full, and when we remove elements from the front since last and first positions are connected, we can insert the elements at the rear which was vacated by deleting the element. Circular queue avoids the wastage of space in a regular queue implementation using arrays.
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