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。