Dch19990825的博客

容斥的几种写法 容斥公式本身就是 枚举出状态的组合，算其乘积，奇数个值为负，偶数个值为正 原理： 对于组合中每个状态有 在或不在两种，求其组合，可以用二进制枚举，也可以用递归 二进制 两层for循环 递归 #include<cstdio> #include<algorithm> #include<string> #incl

G - Visible Trees There are many trees forming a m * n grid, the grid starts from (1,1). Farmer Sherlock is standing at (0,0) point. He wonders how many trees he can see. If two trees and Sherlock are...

F - Co-prime Given a number N, you are asked to count the number of integers between A and B inclusive which are relatively prime to N. Two integers are said to be co-prime or relatively prime if they...