what is circular queue in data structure

Quick Scoop

A circular queue is a queue data structure where the last position connects back to the first, so freed space can be reused instead of wasted. It still follows FIFO: the first item inserted is the first one removed.

How it works

• Enqueue adds an item at the rear.
• Dequeue removes an item from the front.
• When the rear reaches the end, it “wraps around” to the beginning using circular indexing.

Why it matters

In a normal linear queue, empty slots can appear at the front after deletions, but those slots may not be reused. A circular queue fixes that by treating the storage like a ring, which improves space efficiency.

Simple example

If an array queue has size 5 and you remove a few items from the front, a circular queue can place new items into those freed spots instead of stopping just because the rear reached the end. That is the main advantage over a basic queue.

Common uses

Circular queues are often used in buffers, scheduling, and situations where data comes in and out continuously. They are popular because basic operations usually run in constant time.

One-line definition

A circular queue is a FIFO queue that reuses array space by connecting the end back to the start.