用NodeJs实现优先级队列PQueue

优先级队列（PriorityQueue）是个很有用的数据结构，很多编程语言都有实现。NodeJs是一个比较新潮的服务器语言，貌似还没有提供相关类。这些天有用到优先级队列，因为时间很充足，闲来无事，就自己实现了一下。代码如下：

/**
 * script: pqueue.js
 * description: 优先级队列类
 * authors: alwu007@sina.cn
 * date: 2016-04-19
 */
 
var util = require('util');
 
/**
 * 优先级队列类
 * @param cmp_func 优先级比较函数，必需，参考数组排序参数
 */
var PQueue = exports.PQueue = function(cmp_func) {
    //记录数组
    this._records = [];
    //优先级比较方法
    this._cmp_func = cmp_func;
};
 
//堆向上调整
PQueue.prototype._heapUpAdjust = function(index) {
    var records = this._records;
    var record = records[index];
    var cmp_func = this._cmp_func;
    while (index > 0) {
        var parent_index = Math.floor((index - 1) / 2);
        var parent_record = records[parent_index];
        if (cmp_func(record, parent_record) < 0) {
            records[index] = parent_record;
            index = parent_index;
        } else {
            break;
        }
    }
    records[index] = record;
};
 
//堆向下调整
PQueue.prototype._heapDownAdjust = function(index) {
    var records = this._records;
    var record = records[index];
    var cmp_func = this._cmp_func;
    var length = records.length;
    var child_index = 2 * index + 1;
    while (child_index < length) {
        if (child_index + 1 < length && cmp_func(records[child_index], records[child_index + 1]) > 0) {
            child_index ++;
        }
        var child_record = records[child_index];
        if (cmp_func(record, child_record) > 0) {
            records[index] = child_record;
            index = child_index;
            child_index = 2 * index + 1;
        } else {
            break;
        }
    }
    records[index] = record;
};
 
//销毁
PQueue.prototype.destroy = function() {
    this._records = null;
    this._cmp_func = null;
};
 
//将记录插入队列
PQueue.prototype.enQueue = function(record) {
    var records = this._records;
    records.push(record);
    this._heapUpAdjust(records.length - 1);
};
 
//删除并返回队头记录
PQueue.prototype.deQueue = function() {
    var records = this._records;
    if (!records.length)
        return undefined;
    var record = records[0];
    if (records.length == 1) {
        records.length = 0;
    } else {
        records[0] = records.pop();
        this._heapDownAdjust(0);
    }
    return record;
};
 
//获取队头记录
PQueue.prototype.getHead = function() {
    return this._records[0];
};
 
//获取队列长度
PQueue.prototype.getLength = function() {
    return this._records.length;
};
 
//判断队列是否为空
PQueue.prototype.isEmpty = function() {
    return this._records.length == 0;
};
 
//清空队列
PQueue.prototype.clear = function() {
    this._records.length = 0;
};

我觉得，相对于其他排序算法而言，用堆实现优先级队列，入队时间波动较小，比较平稳。