Different Types of Queues

The queue used in the data structure is analogous to a real-world queue. A queue is a type of data structure that follows the FIFO (First-In-First-Out) policy, which states that whatever arrives first will go out first. 

The queue can be described as a list or collection in which insertion occurs from the back end or tail of the queue, and deletion occurs from the front end or head of the queue. It can be compared to a ticket queue outside a cinema theatre. The person who arrives first to join the queue receives the ticket first, and the person who comes last gets the ticket last. This article includes the different types of queues in data structures, such as priority queues, circular queues, etc

Different Types of Queues in Data Structure

Simple Queue or Linear Queue

Linear queue inserts from one end while deletes from the other. Insertion occurs at the back end, while deletion occurs at the front end, following the FIFO principle.

The disadvantage of a linear queue is that insertion happens only from the back end. Even if space is available in a linear queue, we cannot insert new elements if the first three components are eliminated from the queue. The linear queue displays the overflow situation in this example since the back points to the queue’s final member.

Circular Queue

In a circular queue, all nodes are circular. It is identical to a linear queue, except that the last part of the queue is connected to the first. A circular queue is also a ring buffer since all ends are linked. 

A circular queue can do what a linear queue can’t. If there is a space in a circular queue, the new element can be added by simply increasing the value of the rear. A circular queue allows greater memory use.

Priority Queue

As the name goes, in a priority queue, components are arranged as per their importance. Each piece in a priority queue is assigned a priority. Features with the same priority are sorted using the FIFO principle.

Priority queues are most commonly used to create CPU scheduling algorithms.

Two Types of Priority Queues

• In an ascending priority queue, components can be entered in any order, but only the smallest can be eliminated first. Assume an array with elements 7, 5, and 3 in that order. In this queue, insertion can be done using the same sequence, but elements are removed in the order of 3, 5, and 7
• Elements can be put in any sequence in a descending priority queue, but only the most prominent member can be eliminated first. Assume an array with elements 7, 3, and 5 in that exact order. Inserting this queue can be done with the same sequence, but the deletion order should be 7, 5, and 3

Dequeue (Double-Ended Queue)

The dequeue can be used as a stack and a queue because it supports insertion and deletion on both ends. Deque may be compared to a stack since stacks adhere to the LIFO (Last In First Out) principle, where insertion and deletion can only be performed from one end.

With dequeue, both insertion and deletion can be performed from one end. Thus dequeue does not adhere to the FIFO concept.

Two Types of Dequeue

• Input-restricted Dequeue: As the name says, insertion operations may only be conducted at one end of a restricted input queue, but deletion can be performed from both ends
• Output-restricted dequeue: Here, deletion can only be conducted at one end of a restricted output queue, although insertion operations can be performed from both ends

Conclusion

The queue data structure is a linear data structure used to hold items. In programming, a queue is an important data structure. Elements in this data structure are stored using the FIFO approach. 

There are four types of queues in a data structure: linear queue, circular queue, priority queue, and de-queue. Linear Queue inserts from one end while deletes from the other. In a circular queue, all nodes are circular. It is identical to a linear queue, except the last member is connected to the first. In a priority queue, the components are arranged according to their priority. De-queue can be used as a stack and a queue because it supports insertion and deletion on both ends.