实现原理: 1.利用Stack的先进后出的特性,实现一个MaxStack,MaxStack中用一个Stack记录当前的值,一个Stack记录当前的最大值. 2.用2个MaxStack实现MaxQueue,其中一个MaxStack记录出栈记录,一个MaxStack记录入栈记录,取2个MaxStack中的最大值作为当前MaxQueue的最大值. using System; using System.Data; using System.Collections; using System.Collec
需求:取stock表中id最大值+1,作为下一个id值. 特殊情况:考虑到表中会没有值,max(id)会返回空,因此需要用case when进行判断. 实现一:select (case max(id) is null when true then 0 else max(id)+1 end) from stock 实现二:select (case (select count(*) from stock) when 0 then 0 else max(id)+1 end) from stock 效率
198. House Robber You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of them is that adjacent houses have security system connected
一.内置函数补充1.callable()检测传递的参数是否可以被调用.def f1() pass可以被调用f2 = 123不可以被调用2.chr()和ord()chr()将ascii码转换成字符,ord()将字符转换成acsii码在2.7中chr()和ord()用来翻译参数和ascii码的对应关系.例:r = chr(65)print(r)和r = ord("B")print(r)实例:随机验证码import random #用来生成随机数的模块li = []for i in rang
如下图, 计划实现 :按照 parent_code 分组, 取组中code最大值所在的整条记录,如红色部分.(类似hive中: row_number() over(partition by)) select c.* from ( end) as sort_num,(@key_i:=parent_code) as tmp ,@key_i:='') b order by parent_code,code desc) c ; 个人理解, mysql 运行顺序: from >> where >