Queues

A queue is a linear data structure that follows the First-In, First-Out (FIFO) principle. This means that the first element added to the queue is the first one to be removed. Queues are often used to manage tasks or items in a sequential order.


Components of a Queue:

  1. Elements: These are the individual data items stored in the queue.
  2. Front: This is the reference to the front element of the queue, which is the element that has been in the queue the longest and is next to be removed.
  3. Rear (or Back): This is the reference to the rear element of the queue, which is the element that has been in the queue the shortest time and is last to be removed.

Basic Operations on Queues:

  • Enqueue: This operation adds an element to the rear of the queue.
  • Dequeue: This operation removes and returns the front element of the queue.
  • Front (Peek): This operation returns the front element without removing it.
  • isEmpty: This operation checks whether the queue is empty.

Common Use Cases:

  • Breadth-First Search (BFS): Queues are used in graph traversal algorithms like BFS to explore nodes in a level-wise manner.
  • Task Scheduling: Queues are used to manage tasks in a sequential order, such as in job scheduling or managing print jobs in a printer queue.
  • Data Buffering: Queues can be used to buffer data between two processes or threads, ensuring smooth communication.
  • Print Spooling: When multiple documents are sent to a printer, they are placed in a queue (print queue) and printed one after another in the order they were received.
  • Call Center Systems: Queues are used to manage customer support requests, with calls being answered in the order they were received.
  • Message Queues: In distributed systems, message queues are used for communication between different components or services, ensuring reliable message delivery.