function PriorityQueue(maxLength = null,sortFlag="min") {
    this.val = [];
    this.maxLength = maxLength;//队列的最大长度
    this.sortFlag = sortFlag;//最小队列（min),最大队列(max)
    return this;
}

//入队元素(在尾部加入新元素后，做上浮调整)
PriorityQueue.prototype.enQueue = function (val) {
    this.val.push(val);
    this.upAdjust();
}

//删除元素
PriorityQueue.prototype.delQueue = function () {
    if (this.val.length === 0) {
       throw new Error('队列已经是空的')
    }
    //获取堆顶元素
    let head = this.val[0];
    //让最后一个元素移动到堆顶；
    this.val[0] = this.val[this.val.length - 1];
    //下沉调整
    this.downAdjust();
    return head;
}

//上浮调整
PriorityQueue.prototype.upAdjust = function () {
    let childIndex = this.val.length - 1;//从最后一个元素开始调整
    let parentIndex = Math.floor((childIndex - 1) / 2)> 0 ? Math.floor((childIndex - 1) / 2) : 0;//左节点：2*parent + 1
    // temp用于保存插入的节点值，用于最后的赋值
    let temp = this.val[childIndex];
    if (this.sortFlag === "min") {//最小优先队列
        while (childIndex > 0 && temp < this.val[parentIndex]) {
            this.val[childIndex] = this.val[parentIndex];
            childIndex = parentIndex;
            parentIndex = Math.floor(parentIndex / 2) > 0 ? Math.floor(parentIndex / 2) : 0;
        }
        this.val[childIndex] = temp;
    } else {//最大优先队列
        while (childIndex > 0 && temp > this.val[parentIndex]) {
            this.val[childIndex] = this.val[parentIndex];
            childIndex = parentIndex;
            parentIndex = Math.floor(parentIndex / 2)  > 0 ? Math.floor(parentIndex / 2):0;
        }
        this.val[childIndex] = temp;
    }
    
}

//下沉调整
PriorityQueue.prototype.downAdjust = function () {
    let parentIndex = 0;//从第一个元素开始做下沉调整
    let temp = this.val[parentIndex];
    let childIndex = 2 * parentIndex + 1;//左孩子节点
    while (childIndex < this.val.length) {
        if (this.sortFlag === "min") {//最小优先队列
            if (childIndex + 1 < this.val.length && this.val[childIndex + 1] < this.val[childIndex]) {
                childIndex ++;
            }
            //父节点小于任意个子节点，直接跳出
            if (temp < this.val[childIndex]) break;
            this.val[parentIndex] = this.val[childIndex];
            parentIndex = childIndex;
            childIndex = 2 * parentIndex + 1;
        } else {//最大优先队列
            if (childIndex + 1 < this.val.length && this.val[childIndex + 1] > this.val[childIndex]) {
                childIndex ++
            }
            //父节点最大，直接跳出
            if (temp > this.val[childIndex]) break;

            this.val[parentIndex] = this.val[childIndex];
            parentIndex = childIndex;
            childIndex = 2 * parentIndex + 1;
        }
    }
    this.val[parentIndex] = temp;
}

let queue = new PriorityQueue(3, "max");
queue.enQueue(1)
queue.enQueue(5)
queue.enQueue(8)
queue.enQueue(4)
console.log(queue.val) // [ 8, 4, 5, 1 ]


let min_queue = new PriorityQueue(3, "min");
min_queue.enQueue(1)
min_queue.enQueue(5)
min_queue.enQueue(8)
min_queue.enQueue(4)
console.log(min_queue.val)//[ 1, 4, 8, 5 ]