Queues

A queue is a linear data structureThe organisation and order of information in a text. that follows the First In First Out (FIFO) principle. It consists of a collection of elements, where the first element added to the queue is the first one to be removed. The front of the queue is the element that is most likely to be removed next, and the rear of the queue is where new elements are added.

There are three main operations that can be performed on a queue: enqueue, dequeue, and peek.

• The enqueue operation adds an element to the rear of the queue.
• The dequeue operation removes the front element from the queue.
• The peek operation returns the front element of the queue without removing it.

Queues can be represented using an array or a linked list. The array representation is a fixed-size array and the linked list representation is a singly linked list with a head pointing to the front of the queue and a tail pointing to the rear of the queue.

Queues are commonly used in a wide range of applications, some of the most common uses are:

Scheduling: Queues are used in scheduling algorithms to keep track of the order in which tasks need to be executed. The tasks that need to be executed first are added to the front of the queue, and as tasks are completed, they are removed from the front of the queue.

Simulations: Queues are used in simulations to model real-life scenarios such as waiting lines, traffic, and network packets. In these scenarios, elements are added to the rear of the queue, and as they are processed, they are removed from the front of the queue.

Breadth-first search: In breadth-first search algorithm, a queue is used to keep track of the nodes that need to be visited. The first visited node is dequeued, and its children are enqueued to be visited later.