使用javaScript实现一个双端队列

1.双端队列，一种允许我们从队列的前面和后面添加和删除元素的队列。

2.创建一个双端队列的类

class Deque{
    constructor(){
        this.lowestCount = 0;
        this.count = 0;
        this.items = {};
    }
}

3.判断队列是否为空

    isEmpty(){
        return this.size() === 0;
    }

4.获取队列的长度

    size(){
        return this.count - this.lowestCount;
    }

5.从队列头部添加元素

    addFront(element){
        if(this.size()==0){
            addBack(element);
        }else if(this.lowestCount>0){
            this.lowestCount--;
            this.items[this.lowestCount] = element;
        }else{
            for(let i = this.count; i > 0; i++){
                this.items[i] = this.items[i - 1];
            }
            this.count++;
            this.lowestCount = 0;
            this.items[0] = element;
        }
    }

 6.从队列尾部添加元素

    addBack(element){
        this.items[this.count] = element;
        this.count++;
    }

7.查看队列头部元素

    peekFront(){
        return this.items[this.lowestCount];
    }

8.查看队列尾部元素

    peekBack(){
        return this.items[this.count-1];
    }

9.移除队列头部元素

    removeFront(){
        if(this.isEmpty()) return 'queue is null';
        let result = this.items[this.lowestCount];
        delete this.items[this.lowestCount];
        this.lowestCount++;
        return result;
    }

10.移除队列尾部元素

    removeBack(){
        if(this.isEmpty())return "deque is null";
        this.count--;
        let result = this.items[this.count];
        delete this.items[this.count];
        return result;
    }

11.打印队列的所有元素

    toString(){
        if(this.isEmpty())return 'deque is null';
        let objString = `${this.items[this.lowestCount]}`;
        for(let i = this.lowestCount+1;i < this.count; i++){
            objString = `${objString},${this.items[i]}`;
        }
        return objString;
    }

12.清除队列的元素

    clear(){
        this.count = 0;
        this.lowestCount = 0;
        this.items = {};
    }

13.完整代码

class Deque{
    constructor(){
        this.lowestCount = 0;
        this.count = 0;
        this.items = {};
    }
    isEmpty(){
        return this.size() === 0;
    }
    size(){
        return this.count - this.lowestCount;
    }
    addFront(element){
        if(this.size()==0){
            addBack(element);
        }else if(this.lowestCount>0){
            this.lowestCount--;
            this.items[this.lowestCount] = element;
        }else{
            for(let i = this.count; i > 0; i++){
                this.items[i] = this.items[i - 1];
            }
            this.count++;
            this.lowestCount = 0;
            this.items[0] = element;
        }
    }
    addBack(element){
        this.items[this.count] = element;
        this.count++;
    }
    peekFront(){
        return this.items[this.lowestCount];
    }
    peekBack(){
        return this.items[this.count-1];
    }
    removeFront(){
        if(this.isEmpty()) return 'queue is null';
        let result = this.items[this.lowestCount];
        delete this.items[this.lowestCount];
        this.lowestCount++;
        return result;
    }
    removeBack(){
        if(this.isEmpty())return "deque is null";
        this.count--;
        let result = this.items[this.count];
        delete this.items[this.count];
        return result;
    }
    toString(){
        if(this.isEmpty())return 'deque is null';
        let objString = `${this.items[this.lowestCount]}`;
        for(let i = this.lowestCount+1;i < this.count; i++){
            objString = `${objString},${this.items[i]}`;
        }
        return objString;
    }
    clear(){
        this.count = 0;
        this.lowestCount = 0;
        this.items = {};
    }
}

14.结果