【欧拉函数】 HDOJ 2588 GCD

累加n的约数的倍数的欧拉函数即可。。

#include <iostream>  #include <queue>  #include <stack>  #include <map>  #include <set>  #include <bitset>  #include <cstdio>  #include <algorithm>  #include <cstring>  #include <climits>  #include <cstdlib>#include <cmath>#include <time.h>#define maxn 1005#define maxm 40005#define eps 1e-10#define mod 1000000007#define INF 999999999#define lowbit(x) (x&(-x))#define mp mark_pair#define ls o<<1#define rs o<<1 | 1#define lson o<<1, L, mid  #define rson o<<1 | 1, mid+1, R  typedef long long LL;//typedef int LL;using namespace std;LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}void scanf(int &__x){__x=0;char __ch=getchar();while(__ch==' '||__ch=='\n')__ch=getchar();while(__ch>='0'&&__ch<='9')__x=__x*10+__ch-'0',__ch = getchar();}LL gcd(LL _a, LL _b){if(!_b) return _a;else return gcd(_b, _a%_b);}// headint p[maxn];int n, m;int phi(int x){int tmp = sqrt(x), ans = x;for(int i = 2; i <= tmp; i++)if(x % i == 0) {ans -= ans/i;while(x%i == 0) x/=i;}if(x > 1) ans -= ans/x;return ans;}void work(void){int tmp = sqrt(n), cnt = 0;for(int i = 1; i <= tmp; i++)if(n % i == 0) {p[++cnt] = i;if(i * i != n) p[++cnt] = n/i;}int ans = 0;for(int i = 1; i <= cnt; i++)if(p[i] >= m) ans += phi(n/p[i]);printf("%d\n", ans);}int main(void){int _;while(scanf("%d", &_)!=EOF) {while(_--) {scanf("%d%d", &n, &m);work();}}return 0;}