//计算并输出给定10个数的方差. #include<math.h> #include<stdio.h> ]) { double p = 0.0,f=0.0,g=0.0; ; i < ; i++) { p += x[i]; } p = p / ; printf("%f\n", p); ; j < ; j++) { g = x[j] - p; f += g*g; printf("%f\n", f); } f = f / ; f =
大数据计算:如何仅用1.5KB内存为十亿对象计数 Big Data Counting: How To Count A Billion Distinct Objects Using Only 1.5K This is a guest post by Matt Abrams (@abramsm), from Clearspring, discussing how they are able to accurately estimate the cardinality of sets with bi
Mysql每天执行计划,保留最新的10条数据,其余的删除 1.Mysql 保留最新的10条数据 sql语句: DELETE tb FROM tbname AS tb,( SELECT id FROM tbname ORDER BY id desc LIMIT 9,1 ) AS tmp WHERE tb.id<tmp.id 2.新建存储过程(Navicat中) CREATE PROCEDURE test() BEGIN DELETE tb FROM testdata AS tb,( SELECT