design-circular-queue.js

/**
 * Initialize your data structure here. Set the size of the queue to be k.
 * @param {number} k
 */
var MyCircularQueue = function(k) {
  this.data = Array(k);
  this.size = k;
  this.front = 0;
  this.back = 0;
  this.empty = true;
};

/**
 * Insert an element into the circular queue. Return true if the operation is successful.
 * @param {number} value
 * @return {boolean}
 */
MyCircularQueue.prototype.enQueue = function(value) {
  if (this.front === this.back && this.empty === false) return false; // queue is full
  this.data[this.back] = value;
  this.back = (this.back + 1) % this.size;
  this.empty = false;
  return true;
};

/**
 * Delete an element from the circular queue. Return true if the operation is successful.
 * @return {boolean}
 */
MyCircularQueue.prototype.deQueue = function() {
  if (this.empty === true) return false;
  this.data[this.front] = undefined;
  this.front = (this.front + 1) % this.size;
  if (this.back === this.front) this.empty = true;
  return true;
};

/**
 * Get the front item from the queue.
 * @return {number}
 */
MyCircularQueue.prototype.Front = function() {
  if (this.empty === true) return -1;
  return this.data[this.front];
};

/**
 * Get the last item from the queue.
 * @return {number}
 */
MyCircularQueue.prototype.Rear = function() {
  if (this.empty === true) return -1;
  const index = this.back !== 0 ? this.back - 1 : this.size - 1;
  return this.data[index];
};

/**
 * Checks whether the circular queue is empty or not.
 * @return {boolean}
 */
MyCircularQueue.prototype.isEmpty = function() {
  return this.empty;
};

/**
 * Checks whether the circular queue is full or not.
 * @return {boolean}
 */
MyCircularQueue.prototype.isFull = function() {
  return this.front === this.back && this.empty === false;
};

/**
 * 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()
 */