What is a Queue?

A queue is a linear data structure that follows the FIFO (First In, First Out) principle. This means that the element added first will be the first one to be removed, similar to a queue in real life (like waiting in line for a ticket).

Front and Rear in a Queue

• Front: The index where elements are removed from the queue.
• Rear: The index where new elements are inserted into the queue.
• When the queue is empty, both front and rear are set to -1.
• When an element is added, the rear moves forward.
• When an element is removed, the front moves forward.

Enqueue (Insertion in Queue)

• When adding an element, we insert it at the rear position.
• If the queue is empty, both front and rear are set to 0.
• The rear pointer increases by 1 with each new element.
• If rear reaches the max size of the queue, it causes a Queue Overflow (meaning no more elements can be added).

🔹 Dequeue (Removing an Element from Queue)

• The element at the front is removed.
• The front pointer moves forward by 1.
• If front > rear, the queue is empty, causing Queue Underflow (no elements left to remove).
• In a regular queue, removed elements leave empty spaces, reducing efficiency. Circular queues solve this issue.