题目

https://leetcode.cn/problems/design-circular-deque/description/

存储循环队列的向量空间是循环的，用通俗的话来讲，就是我们在做next或者prev操作时，不会发生溢出
取模、或者直接判断是否为0/size返回一个值。

数组实现

用函数来实现一个类，定义容量、头尾指针，和初始化数组存储

/*** @param {number} k*/
var MyCircularDeque = function(k) {this.capacity = k + 1;this.rear = this.front = 0;this.elements = new Array(k + 1).fill(0);
};

利用原型链扩展循环队列的能力

/** * @param {number} value* @return {boolean}*/
MyCircularDeque.prototype.insertFront = function(value) {if (this.isFull()) {return false;}this.front = (this.front - 1 + this.capacity) % this.capacity;this.elements[this.front] = value;return true;
};/** * @param {number} value* @return {boolean}*/
MyCircularDeque.prototype.insertLast = function(value) {if (this.isFull()) {return false;}this.elements[this.rear] = value;this.rear = (this.rear + 1) % this.capacity;return true;
};/*** @return {boolean}*/
MyCircularDeque.prototype.deleteFront = function() {
if (this.isEmpty()) {return false;}this.front = (this.front + 1) % this.capacity;return true;
};/*** @return {boolean}*/
MyCircularDeque.prototype.deleteLast = function() {
if (this.isEmpty()) {return false;}this.rear = (this.rear - 1 + this.capacity) % this.capacity;return true;
};/*** @return {number}*/
MyCircularDeque.prototype.getFront = function() {if (this.isEmpty()) {return -1;}return this.elements[this.front];
};/*** @return {number}*/
MyCircularDeque.prototype.getRear = function() {
if (this.isEmpty()) {return -1;}return this.elements[(this.rear - 1 + this.capacity) % this.capacity];
};/*** @return {boolean}*/
MyCircularDeque.prototype.isEmpty = function() {
return this.rear == this.front;
};/*** @return {boolean}*/
MyCircularDeque.prototype.isFull = function() {return (this.rear + 1) % this.capacity == this.front;
};/*** Your MyCircularDeque object will be instantiated and called as such:* var obj = new MyCircularDeque(k)* var param_1 = obj.insertFront(value)* var param_2 = obj.insertLast(value)* var param_3 = obj.deleteFront()* var param_4 = obj.deleteLast()* var param_5 = obj.getFront()* var param_6 = obj.getRear()* var param_7 = obj.isEmpty()* var param_8 = obj.isFull()*/