19. DSA with C++ - Queue data structure

Queue

Introduction: A queue is an abstract data type that follows the First-In-First-Out (FIFO) principle. It is a collection of elements in which the first element inserted is the first one to be removed. A queue has the following properties:

1. FIFO Order: The most significant property of a queue is the FIFO order. The first element inserted into the queue is the first one to be removed. It follows the "first in, first out" behavior.
2. Enqueue Operation: The enqueue operation adds an element to the back of the queue. It inserts an element into the queue.
3. Dequeue Operation: The dequeue operation removes the front element from the queue. It deletes the element that was first inserted.
4. Peek/Front Operation: The peek operation returns the front element of the queue without removing it. It allows you to access the element at the front of the queue without modifying the queue itself.
5. Queue Size: The queue can have a limited size or be implemented with dynamic memory allocation, allowing it to grow or shrink as needed.

Queues can be implemented using various data structures such as arrays or linked lists. The choice of implementation depends on the requirements and constraints of the problem at hand. Some common applications of queues include process scheduling, task management, breadth-first search algorithms, buffer management, and handling requests in networking.

Queues have efficient time complexities for their operations:

- Enqueue operation: O(1)
- Dequeue operation: O(1)
- Peek/Front operation: O(1)

Overall, the properties and operations of a queue make it a useful data structure in situations where the order of element access and removal follows the FIFO principle.