【前端面试】设计循环双端队列javascript

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()
 */