http://acm.hdu.edu.cn/showproblem.php?pid=6390 题意:求一个式子 题解:看题解,写代码 第一行就看不出来,后面的sigma公式也不会化简.mobius也不会 就自己写了个容斥搞一下(才能维持现在的生活) //别人的题解https://blog.csdn.net/luyehao1/article/details/81672837 #include <iostream> #include <cstdio> #include <cstr…

Given a positive integer N, your task is to calculate the sum of the positive integers less than N which are not coprime to N. A is said to be coprime to B if A, B share no common positive divisors except 1. InputFor each test case, there is a line c…

题面: 题解:欧拉函数的基础应用,再套个很 easy 的等差数列前 n 项和就成了. 啊,最近在补作业+准备月考+学数论,题就没怎么写,感觉菜得一匹>_< CSL加油加油~! 代码: #include<cstdio> #include<cmath> #define ll long long #define mod(a) ((a)>=MOD?(a)%MOD:(a)) using namespace std; ; ll N,sq,phi,n; int main(){…

裸题 O(nlogn): #include <cstdio> #include <iostream> #include <algorithm> using namespace std; typedef long long ll; const int maxn=3000000+100; int phi[maxn]; void init() { for(int i=2;i<maxn;i++) phi[i]=i; for(int i=2;i<maxn;i++) i…

Become A Hero Time Limit: 15000/5000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 210    Accepted Submission(s): 57 Problem Description Lemon wants to be a hero since he was a child. Recently he is reading a book…

The Euler function Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 5235    Accepted Submission(s): 2225 Problem Description The Euler function phi is an important kind of function in number theo…

2^x mod n = 1 Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)Total Submission(s): 15810    Accepted Submission(s): 4914 Problem Description Give a number n, find the minimum x(x>0) that satisfies 2^x mod n = 1.   I…

图(无向图或有向图)中恰好通过所有边一次且经过所有顶点的的通路成为欧拉通路,图中恰好通过所有边一次且经过所有顶点的回路称为欧拉回路,具有欧拉回路的图称为欧拉图,具有欧拉通路而无欧拉回路的图称为半欧拉图. 规定平凡图(只有一个点)是欧拉图. 性质与定理: 无向图G是欧拉图当且仅当G是连通的且没有奇度顶点. 无向图G是半欧拉图当且仅当G是连通的且恰有两个奇度顶点. 有向图D是欧拉图当且仅当D是强连通的且每个顶点恰有两个奇度顶点. 有向图D是半欧拉图当且仅当D是单连通的且每个顶点入度等于出度. 显然,…

Description has only two Sentences Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)Total Submission(s): 1071    Accepted Submission(s): 323 Problem Description an = X*an-1 + Y and Y mod (X-1) = 0.Your task is to cal…

题意:求树上任意两点的距离 先说下欧拉序 对这颗树来说 欧拉序为 ABDBEGBACFHFCA 那欧拉序有啥用 这里先说第一个作用 求lca 对于一个欧拉序列,我们要求的两个点在欧拉序中的第一个位置之间肯定包含他们的lca,因为欧拉序1上任意两点之间肯定包含从第一个点走到第二个点访问的路径上的所有点 所以只需要记录他们的深度,然后从两个询问子节点x,y第一次出现的位置之间的深度最小值即可,可能不大好理解,看张图吧. 也就是说求lca可以转换为求一段区间的最值问题,结合rmq就可以处理啦 对于25…