622. Design Circular Queue

Design your implementation of the circular queue. The circular queue is a linear data structure in which the operations are performed based on FIFO (First In First Out) principle, and the last position is connected back to the first position to make a circle. It is also called "Ring Buffer".

One of the benefits of the circular queue is that we can make use of the spaces in front of the queue. In a normal queue, once the queue becomes full, we cannot insert the next element even if there is a space in front of the queue. But using the circular queue, we can use the space to store new values.

Implement the MyCircularQueue class:

• MyCircularQueue(k) Initializes the object with the size of the queue to be k.

• int Front() Gets the front item from the queue. If the queue is empty, return -1.

• int Rear() Gets the last item from the queue. If the queue is empty, return -1.

• boolean enQueue(int value) Inserts an element into the circular queue. Return true if the operation is successful.

• boolean deQueue() Deletes an element from the circular queue. Return true if the operation is successful.

• boolean isEmpty() Checks whether the circular queue is empty or not.

• boolean isFull() Checks whether the circular queue is full or not.

class MyCircularQueue {

    private int[] queue;
    private int front, rear;
    private int length;

    public MyCircularQueue(int k) {
        this.queue = new int[k];
        this.front = 0;
        this.rear = -1;
        this.length = 0;
    }
    
    public boolean enQueue(int value) {
        if (isFull()) return false;
        // add element from back
        // if queue has empty space at front, it will be added to the front empty space
        rear = (rear + 1) % queue.length; 
        queue[rear] = value;
        length++;
        return true;
    }
    
    public boolean deQueue() {
        if (isEmpty()) return false;
        front = (front + 1) % queue.length; // get element from front so we move the front pointer
        length--;
        return true;
    }
    
    public int Front() {
        return isEmpty() ? -1 : queue[front];
    }
    
    public int Rear() {
        return isEmpty() ? -1 : queue[rear];
    }
    
    public boolean isEmpty() {
        return length == 0;
    }
    
    public boolean isFull() {
        return length == queue.length;
    }
}