Design Circular Queue

Description

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]
Explanation
MyCircularQueue myCircularQueue = new MyCircularQueue(3);
myCircularQueue.enQueue(1); // return True
myCircularQueue.enQueue(2); // return True
myCircularQueue.enQueue(3); // return True
myCircularQueue.enQueue(4); // return False
myCircularQueue.Rear();     // return 3
myCircularQueue.isFull();   // return True
myCircularQueue.deQueue();  // return True
myCircularQueue.enQueue(4); // return True
myCircularQueue.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.

Solution(javascript)

/**
 * @param {number} k
 */
var MyCircularQueue = function(k) {
    this.que = new Array(k).fill(-1);
    this.front = -1;
    this.rear = -1;
};

/** 
 * @param {number} value
 * @return {boolean}
 */
MyCircularQueue.prototype.enQueue = function(value) {
     if(this.rear == -1 && this.front == -1){
        this.rear=0;
        this.front=0;
        this.que[0]=value;
        return true;
    }
    else{
        
        if((this.rear + 1) % this.que.length == this.front)
            return false;
        else{
            this.rear=(this.rear + 1) % this.que.length;
            this.que[this.rear]=value;
            return true;
        }
    }
};

/**
 * @return {boolean}
 */
MyCircularQueue.prototype.deQueue = function() {
    if(this.rear == -1 && this.front == -1){
        return false;
    }
    else if(this.rear==this.front){
        this.que[this.front]=-1;
        this.front=-1;
        this.rear=-1;
        return true;
    }
    else{        
        this.que[this.front]=-1;
        this.front=(this.front+1)%this.que.length;
        return true;
    }  
};

/**
 * @return {number}
 */
MyCircularQueue.prototype.Front = function() {
    if(this.front != -1) return this.que[this.front];
    return -1;
};

/**
 * @return {number}
 */
MyCircularQueue.prototype.Rear = function() {
    if(this.rear!=-1) return this.que[this.rear];
    return -1;
};

/**
 * @return {boolean}
 */
MyCircularQueue.prototype.isEmpty = function() {
    return this.front==-1;

};

/**
 * @return {boolean}
 */
MyCircularQueue.prototype.isFull = function() {
    return this.front!=-1&&this.front==(this.rear+1)%this.que.length;
};

/** 
 * 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()
 */