What is a circular queue?

Java MCQ: What is a circular queue?

Answer:

Explanation:

A circular queue is a linear data structure in which the operations are performed based on the FIFO principle, and the last position is connected back to the first position to form a circle. This structure helps to efficiently utilize space by allowing the queue to reuse empty slots left behind when elements are dequeued.

In a standard linear queue, once the rear pointer reaches the end of the queue, no more elements can be added even if there are empty slots at the front due to dequeued elements. A circular queue overcomes this limitation by wrapping around to the beginning of the queue, thus making efficient use of the available space.

Here’s an example of a circular queue implementation in Java:

class CircularQueue {
    private int[] queue;
    private int front, rear, size;

    public CircularQueue(int capacity) {
        queue = new int[capacity];
        front = rear = size = 0;
    }

    public void enqueue(int value) {
        if (size == queue.length) {
            System.out.println("Queue is full");
        } else {
            queue[rear] = value;
            rear = (rear + 1) % queue.length;
            size++;
        }
    }

    public int dequeue() {
        if (size == 0) {
            System.out.println("Queue is empty");
            return -1;
        } else {
            int value = queue[front];
            front = (front + 1) % queue.length;
            size--;
            return value;
        }
    }
}

In this example, the enqueue and dequeue operations utilize modular arithmetic to wrap around the rear and front pointers when they reach the end of the queue array. This allows the circular queue to efficiently manage space and avoid the wastage of slots at the front of the queue.

Reference links:

https://www.javaguides.net/p/java-circular-queue-tutorial.html