UVA12995 Farey Sequence 欧拉函数 同仪仗队那题几乎相同,本质都是求欧拉函数的和 #include<cstdio> #define N 1000000 ],i,j,t; ],s[N+]; ]; int main(){ ;i<=N;++i){ ,pri[++cnt]=i; ;j<=cnt;++j){ t=i*pri[j]; if(t>N) break; v[t]=; ); else{phi[t]=phi[i]*pri[j];break;} } }//线性筛…

洛谷传送门 Farey Sequence (格式太难调,题面就不放了) 分析: 实际上求分数个数就是个幌子,观察可以得到,所求的就是$\sum^n_{i=2}\phi (i)$,所以直接欧拉筛+前缀和即可. Code: #include<cstdio> #include<cstring> #include<cstdlib> #include<cmath> #include<iostream> #include<iomanip> #in…

洛谷题目传送门 分数其实就是一个幌子,实际上就是求互质数对的个数(除开一个特例\((1,1)\)).因为保证了\(a<b\),所以我们把要求的东西拆开看,不就是\(\sum_{i=2}^n\phi(i)\)吗? 关于通过筛素数线性求欧拉函数的一点思路总结在蒟蒻的blog里 剩下的就是记一个前缀和了. #include<cstdio> #define R register const int N=1000001; int pr[N],phi[N]; long long ans[N]; bo…

Farey Sequence 题意:给定一个数n,求在[1,n]这个范围内两两互质的数的个数.(转化为给定一个数n,比n小且与n互质的数的个数) 知识点: 欧拉函数: 普通求法: int Euler(int n) { int ans=n; for(int i=0;i<cnt&&prime[i]<=n;i++) { if(n%prime[i]==0) { ans=ans-ans/prime[i]; while(n%prime[i]==0) n/=prime[i]; } } if(…

 名字是法雷数列其实是欧拉phi函数              Farey Sequence Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 11246   Accepted: 4363 Description The Farey Sequence Fn for any integer n with n >= 2 is the set of irreducible rational numbers a/b with 0 <…

Description The Farey Sequence Fn for any integer n with n >= 2 is the set of irreducible rational numbers a/b with 0 < a < b <= n and gcd(a,b) = 1 arranged in increasing order. The first few are  F2 = {1/2}  F3 = {1/3, 1/2, 2/3}  F4 = {1/4, 1…

A - Farey Sequence Time Limit:1000MS     Memory Limit:65536KB     64bit IO Format:%I64d & %I64u Submit Status Practice POJ 2478 Description The Farey Sequence Fn for any integer n with n >= 2 is the set of irreducible rational numbers a/b with 0 &l…

题目大意 直接看原文吧.... The Farey Sequence Fn for any integer n with n >= 2 is the set of irreducible rational numbers a/b with 0 < a < b <= n and gcd(a,b) = 1 arranged in increasing order. The first few areF2 = {1/2}F3 = {1/3, 1/2, 2/3}F4 = {1/4, 1/3…

The Farey Sequence Fn for any integer n with n >= 2 is the set of irreducible rational numbers a/b with 0 < a < b <= n and gcd(a,b) = 1 arranged in increasing order. The first few are F2 = {1/2} F3 = {1/3, 1/2, 2/3} F4 = {1/4, 1/3, 1/2, 2/3, 3…

The Farey Sequence Fn for any integer n with n >= 2 is the set of irreducible rational numbers a/b with 0 < a < b <= n and gcd(a,b) = 1 arranged in increasing order. The first few are F2 = {1/2} F3 = {1/3, 1/2, 2/3} F4 = {1/4, 1/3, 1/2, 2/3, 3…