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…

Farey Sequence Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 18507   Accepted: 7429 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)…

题目链接: Farey Sequence Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 14230   Accepted: 5624 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 - 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…

题目链接:http://poj.org/problem?id=2478 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}…

一.题目 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…

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…

题目链接:http://poj.org/problem?id=2478 Farey Sequence Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 19736   Accepted: 7962 Description The Farey Sequence Fn for any integer n with n >= 2 is the set of irreducible rational numbers a/b with…

题意:给出式子F F中分子分母互质,且分子小于分母 例: F2 = {1/2} F3 = {1/3, 1/2, 2/3} F4 = {1/4, 1/3, 1/2, 2/3, 3/4} F5 = {1/5, 1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5} 求解 fn的元素个数. 分析:本题就是求解欧拉函数值的前n项和,直接求解欧拉函数值的方法不行,由于用此法就是O(n^2)复杂度.採用递推式求解是O(nlogn)复杂度 代码例如以下: #include <set>…

题意:给定一个数 n,问你0<= a <=n, 0 <= b <= n,有多少个不同的最简分数. 析:这是一个欧拉函数题,由于当时背不过模板,又不让看书,我就暴力了一下,竟然AC了,才2s,题目是给了3s,很明显是由前面递推,前面成立的,后面的也成立, 只要判定第 i 个有几个,再加前 i-1 个就好,第 i 个就是判断与第 i 个互质的数有多少,这就是欧拉函数了. 代码如下: 这是欧拉函数的. #pragma comment(linker, "/STACK:102400…