UVA - 10820 - Send a Table

来源：互联网发布：ggplot2 python 编辑：程序博客网时间：2024/04/26 11:39

题意：1 <= x, y <= n，可以根据 f（x0, y0）得知 f（k * x0, k * y0），问最简要得知所有的f（x，y）至少需要统计多少x与y？

可以看出，实质就是与，n以内有多少对互素的元素，利用欧拉函数即可。

#include<cstdio>#include<cstring>#include<cctype>#include<cstdlib>#include<cmath>#include<iostream>#include<sstream>#include<iterator>#include<algorithm>#include<string>#include<vector>#include<set>#include<map>#include<deque>#include<queue>#include<stack>#include<list>typedef long long ll;typedef unsigned long long llu;const int MAXN = 100 + 10;const int MAXT = 50000 + 10;const int INF = 0x7f7f7f7f;const double pi = acos(-1.0);const double EPS = 1e-6;using namespace std;int a[MAXT], phi[MAXT];//欧拉函数打表void phi_table(){    memset(phi, 0, sizeof phi);    phi[1] = 1;    for(int i = 2; i < MAXT; ++i)        if(!phi[i])            for(int j = i; j < MAXT; j += i){                if(!phi[j])  phi[j] = j;                phi[j] = phi[j] / i * (i - 1);            }    for(int i = 3; i < MAXT; ++i)  phi[i] += phi[i - 1];}int main(){    phi_table();    int n;    while(scanf("%d", &n) == 1 && n){        if(n == 1)  printf("1\n");        else  printf("%d\n", 2 * phi[n] + 1);    }    return 0;}

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