E. Sum of Remainders time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Calculate the value of the sum: n mod 1 + n mod 2 + n mod 3 + ... + n mod m. As the result can be very large, you shoul…

616E Sum of Remainders Calculate the value of the sum: n mod 1 + n mod 2 + n mod 3 + - + n mod m. As the result can be very large, you should print the value modulo 109 + 7 (the remainder when divided by 109 + 7). The modulo operator a mod b stands f…

题目链接 给两个数n, m. 求n%1+n%2+.......+n%m的值. 首先, n%i = n-n/i*i, 那么原式转化为n*m-sigma(i:1 to m)(n/i*i). 然后我们可以发现  1/4 = 2/4 = 3/4 = 0, 4/4 = 5/4 = 6/4 = 7/4 = 1. 所以可以将这些结果分成很多块, 按块算结果. 注意计算过程中时刻避免爆longlong. #include <iostream> #include <vector> #include…

题意:定义F(a,0) = 0,F(a,b) = 1 + F(a,b - GCD(a,b).给定 x 和 y (<=1e12)求F(x,y). 题解:a=A*GCD(a,b) b=B*GCD(a,b),那么b-GCD(a,b) = (B-1)*GCD(a,b),如果此时A和B-1依然互质,那么GCD不变下一次还是要执行b-GCD(a,b).那么GCD什么时候才会变化呢?就是说找到一个最小的S,使得(B-S)%T=0其中T是a的任意一个因子.变形得到:B%T=S于是我们知道S=min(B%T).也…

A. Hanoi tower Time Limit: 1 Sec Memory Limit: 256 MB 题目连接 http://codeforces.com/gym/100114 Description you the conditions of this task. There are 3 pivots: A, B, C. Initially, n disks of different diameter are placed on the pivot A: the smallest dis…

BOPCTime Limit: 20 Sec Memory Limit: 256 MB 题目连接 http://acm.hust.edu.cn/vjudge/contest/view.action?cid=86686#problem/D Description You invented a new chess figure and called it BOPC. Suppose it stands at the square grid at the point with coordinates …

一看就是找规律的题.只要熟悉异或的性质,可以秒杀. 为了防止忘记异或的规则,可以把异或理解为半加运算:其运算法则相当于不带进位的二进制加法. 一些性质如下: 交换律: 结合律: 恒等律: 归零律: 典型应用:交换a和b的值:a=a^b^(b=a); #include<iostream> #include<cstdio> #include<cstdlib> #include<cstring> #include<cmath> #include<…

题目描述: Malek Dance Club time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output As a tradition, every year before IOI all the members of Natalia Fan Club are invited to Malek Dance Club to have a fu…

Another Rock-Paper-Scissors Problem 题目连接: http://codeforces.com/gym/100015/attachments Description Sonny uses a very peculiar pattern when it comes to playing rock-paper-scissors. He likes to vary his moves so that his opponent can't beat him with hi…

D. Optimal Number Permutation time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output You have array a that contains all integers from 1 to n twice. You can arbitrary permute any numbers in a. Let…