HDU 1905 Pseudoprime numbers

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根据费马定理当p为素数 a>1时有(a^p)%p==a%p

有少部分非素数对a也能满足该公式这些素数称为a的伪素数问给定的p和a p是不是a的伪素数

快速幂问题

注意p<10^9 可能爆掉int

#include<iostream>#include<cstdlib>#include<cstdio>#include<string>#include<vector>#include<deque>#include<queue>#include<algorithm>#include<set>#include<map>#include<stack>#include<ctime>#include<cmath>#include<list>#include<cstring>//#include<memory.h>using namespace std;#define ll long long#define ull unsigned long long#define pii pair<int,int>#define INF 1000000007#define pll pair<ll,ll>#define pid pair<int,double>#define sci(a) scanf("%d",&a)#define scd(a) scanf("%lf",&a)#define scs(a) scanf("%s",a)#define pri(a) printf("%d\n",a);#define prd4(a) printf("%.4lf\n",a);#define prs(a) printf("%s\n",a);bool isprime(int n){//判断n是否为素数    int end=sqrt(n+1);    for(int i=2;i<=end;++i)        if(n%i==0)            return false;    return true;}int fast_pow(int a,int n,int mod){//快速幂    int res=1;    while(n){        if(n&1)            res=((ll)res*a)%mod;//强制类型转换 防止爆掉        a=((ll)a*a)%mod;        n>>=1;    }    return res;}int main(){    //freopen("/home/lu/文档/r.txt","r",stdin);    //freopen("/home/lu/文档/w.txt","w",stdout);    int p,a;    while(scanf("%d%d",&p,&a),a+p)        prs((!isprime(p)&&fast_pow(a,p,p)==a%p)?"yes":"no");    return 0;}

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