Design Circular Queue

Problem statement

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.

Implementation 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.

You must solve the problem without using the built-in queue data structure in your programming language. 

Example 1:

Input["MyCircularQueue", "enQueue", "enQueue", "enQueue", "enQueue", "Rear", "isFull", "deQueue", "enQueue", "Rear"][[3], [1], [2], [3], [4], [], [], [], [4], []]Output[null, true, true, true, false, 3, true, true, true, 4]ExplanationMyCircularQueue myCircularQueue = new MyCircularQueue(3);myCircularQueue.enQueue(1); // return TruemyCircularQueue.enQueue(2); // return TruemyCircularQueue.enQueue(3); // return TruemyCircularQueue.enQueue(4); // return FalsemyCircularQueue.Rear();     // return 3myCircularQueue.isFull();   // return TruemyCircularQueue.deQueue();  // return TruemyCircularQueue.enQueue(4); // return TruemyCircularQueue.Rear();     // return 4

Constraints:

• 1 <= k <= 1000
• 0 <= value <= 1000
• At most 3000 calls will be made to enQueue, deQueue, Front, Rear, isEmpty, and isFull.

My solution

class Node {
    constructor(val) {
        this.val = val;
        this.next = null
    }
}

/**
 * @param {number} k
 */
var MyCircularQueue = function(k) {
    this.head = null;
    this.tail = null;
    this.maxSize = k;
    this.size = 0;
};

/** 
 * @param {number} value
 * @return {boolean}
 */
MyCircularQueue.prototype.enQueue = function(value) {
    if (this.size === this.maxSize) {
        return false;
    }
    const newNode = new Node(value);
    
    if (!this.head) {
        this.head = newNode;        
        this.tail = newNode;
        newNode.next = this.head;
        this.size++
        return true;
    }
    
//     Make newNode the current tails next node;
    this.tail.next = newNode;
    this.tail = newNode;
    newNode.next = this.head;
    this.size++
    
    return true;
    
};

/**
 * @return {boolean}
 */
MyCircularQueue.prototype.deQueue = function() {
    if (!this.head) {
        return false;
    }
    
    const nodeToDelete = this.head;
    if (this.head) {
        this.size--;
        if (this.size === 0) {
            this.head = null;
            this.tail = null
        } else {
            this.head = this.head.next;
            this.tail.next = this.head;
        }
    } else {
        this.head = null;
        this.tail = null
    }
    return true;
};

/**
 * @return {number}
 */
MyCircularQueue.prototype.Front = function() {
    if (this.head === null) {
        return -1
    }
    return this.head.val;
};

/**
 * @return {number}
 */
MyCircularQueue.prototype.Rear = function() {
    if (this.tail === null) {
        return -1
    }
    return this.tail.val
};

/**
 * @return {boolean}
 */
MyCircularQueue.prototype.isEmpty = function() {
    // console.log("this.size", this.size)
    return this.size === 0
};

/**
 * @return {boolean}
 */
MyCircularQueue.prototype.isFull = function() {
    return this.size === this.maxSize;
};

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