1.背景 想要统计这一个字符串数组中每一个非重复字符串的数量,使用map来保存其key和value.这个需求在实际开发中经常使用到,我以前总是新建一个空数组来记录不重复字符串,并使用计数器计数,效率低下且麻烦,特此记录. 2.代码实现 public class test { public void makeEqual(String[] words) { Map<String,Integer> maps = new HashMap<>(); for (String str : wor
SELECT count(status = 0 OR NULL) AS a, count(status = 1 OR NULL) AS b, count(status = 2 OR NULL) AS c, count(status = 3 OR NULL) AS d, count(status = 4 OR NULL) AS eFROM wx_order;
1.统计每分钟内 url 的访问数量 SELECT SUBSTRING(CONVERT(varchar(100), date, 20), 0,17) as dateTime,COUNT(url) as count,url,referer FROM demo GROUP BY url,(SUBSTRING(CONVERT(varchar(100), date, 20), 0,17) ),referer;
Numpy.frompyfunc()将计算单个值的函数转化为计算数组中每个元素的函数 不再通过遍历,对数组中的元素进行运算,利用frompyfunc()将计算单个值的函数转化为计算数组中每个元素的函数 下面是示例代码: # -*- coding: utf-8 -*- """ Created on Fri Nov 20 17:18:11 2020 @author: pan """ import time import numpy as np arr