设计双端循环队列

2021-03-17

题目描述

设计实现双端队列。
你的实现需要支持以下操作：
MyCircularDeque(k)：构造函数,双端队列的大小为k。
insertFront()：将一个元素添加到双端队列头部。如果操作成功返回 true。
insertLast()：将一个元素添加到双端队列尾部。如果操作成功返回 true。
deleteFront()：从双端队列头部删除一个元素。如果操作成功返回 true。
deleteLast()：从双端队列尾部删除一个元素。如果操作成功返回 true。
getFront()：从双端队列头部获得一个元素。如果双端队列为空，返回 -1。
getRear()：获得双端队列的最后一个元素。如果双端队列为空，返回 -1。
isEmpty()：检查双端队列是否为空。
isFull()：检查双端队列是否满了。

// @lc code=start
/**
 * Initialize your data structure here. Set the size of the deque to be k.
 * @param {number} k
 */
 var MyCircularDeque = function(k) {
    this.head = 0;
    this.tail = 0;
    this.cnt = 0;
    this.items = new Array(k);
};

/**
 * Adds an item at the front of Deque. Return true if the operation is successful. 
 * @param {number} value
 * @return {boolean}
 */
MyCircularDeque.prototype.insertFront = function(value) {
    if (this.isFull()) {
        return false;
    }
    this.head = (this.head - 1 + this.items.length) % this.items.length;
    this.items[this.head] = value;
    this.cnt += 1;
    return true;
};

/**
 * Adds an item at the rear of Deque. Return true if the operation is successful. 
 * @param {number} value
 * @return {boolean}
 */
MyCircularDeque.prototype.insertLast = function(value) {
    if (this.isFull()) {
        return false;
    }
    this.items[this.tail] = value;
    this.tail = (this.tail + 1) % this.items.length;
    this.cnt += 1;
    return true;
};

/**
 * Deletes an item from the front of Deque. Return true if the operation is successful.
 * @return {boolean}
 */
MyCircularDeque.prototype.deleteFront = function() {
    if (this.isEmpty()) {
        return false;
    }
    this.head = (this.head + 1) % this.items.length;
    this.cnt -= 1;
    return true;
};

/**
 * Deletes an item from the rear of Deque. Return true if the operation is successful.
 * @return {boolean}
 */
MyCircularDeque.prototype.deleteLast = function() {
    if (this.isEmpty()) {
        return false;
    }
    this.tail = (this.tail - 1 + this.items.length) % this.items.length;
    this.cnt -= 1;
    return true;
};

/**
 * Get the front item from the deque.
 * @return {number}
 */
MyCircularDeque.prototype.getFront = function() {
    if (this.isEmpty()) {
        return -1;
    }
    return this.items[this.head];
};

/**
 * Get the last item from the deque.
 * @return {number}
 */
MyCircularDeque.prototype.getRear = function() {
    if (this.isEmpty()) {
        return -1;
    }
    return this.items[(this.tail - 1 + this.items.length) % this.items.length];
};

/**
 * Checks whether the circular deque is empty or not.
 * @return {boolean}
 */
MyCircularDeque.prototype.isEmpty = function() {
    return this.cnt === 0;
};

/**
 * Checks whether the circular deque is full or not.
 * @return {boolean}
 */
MyCircularDeque.prototype.isFull = function() {
    return this.cnt === this.items.length;
};