Problem: Design Circular Queue

Question

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.

Your implementation should support following operations:

MyCircularQueue(k): Constructor, set the size of the queue to be k.
Front: Get the front item from the queue. If the queue is empty, return -1.
Rear: Get the last item from the queue. If the queue is empty, return -1.
enQueue(value): Insert an element into the circular queue. Return true if the operation is successful.
deQueue(): Delete an element from the circular queue. Return true if the operation is successful.
isEmpty(): Checks whether the circular queue is empty or not.
isFull(): Checks whether the circular queue is full or not.

Example:

MyCircularQueue circularQueue = new MyCircularQueue(3); // set the size to be 3
circularQueue.enQueue(1);  // return true
circularQueue.enQueue(2);  // return true
circularQueue.enQueue(3);  // return true
circularQueue.enQueue(4);  // return false, the queue is full
circularQueue.Rear();  // return 3
circularQueue.isFull();  // return true
circularQueue.deQueue();  // return true
circularQueue.enQueue(4);  // return true
circularQueue.Rear();  // return 4

Solution

TODO

Code

class MyCircularQueue {
    
    int[] buffer;
    int k;
    int rear;
    int front;

    /** Initialize your data structure here. Set the size of the queue to be k. */
    public MyCircularQueue(int k) {
        buffer = new int[k];
        this.k = k;
        front = 0;
        rear = -1;
    }
    
    /** Insert an element into the circular queue. Return true if the operation is successful. */
    public boolean enQueue(int value) {
        if(isFull()) return false;
        rear++;
        buffer[idx(rear)] = value;
        return true;
    }
    
    /** Delete an element from the circular queue. Return true if the operation is successful. */
    public boolean deQueue() {
        if(isEmpty()) return false;
        front++;
        return true;
    }
    
    /** Get the front item from the queue. */
    public int Front() {
        if(isEmpty()) return -1;
        return buffer[idx(front)];
    }
    
    /** Get the last item from the queue. */
    public int Rear() {
        if(isEmpty()) return -1;
        return buffer[idx(rear)];
    }
    
    /** Checks whether the circular queue is empty or not. */
    public boolean isEmpty() {
        return rear < front;   
    }
    
    /** Checks whether the circular queue is full or not. */
    public boolean isFull() {
        return rear - front == k-1;
    }
    
    private int idx(int i) {
        return i % k;
    }
}

/**
 * Your MyCircularQueue object will be instantiated and called as such:
 * MyCircularQueue obj = new MyCircularQueue(k);
 * boolean param_1 = obj.enQueue(value);
 * boolean param_2 = obj.deQueue();
 * int param_3 = obj.Front();
 * int param_4 = obj.Rear();
 * boolean param_5 = obj.isEmpty();
 * boolean param_6 = obj.isFull();
 */

Performance