UVa10006-Carmichael Numbers

http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=947

快速幂取模

code:

 

#include <iostream>
#include <cstring>
#include <cmath>
using namespace std;
typedef long long LL;
LL pow_mod(LL a, LL b, LL m)
{LL res = 1;for(;b;b>>=1,a=(a*a)%m)if(b&1) res =(res*a) %m;/*while(b){if(b&1) res =res*a %m;a = a*a % m;b >>=1;}*/return res;
}
#define N 65000
bool prime[N];
void sieve_prime()
{memset(prime,1,sizeof(prime));for(int i=2;i<=sqrt(N); i++)if(prime[i])for(int j=i*i; j<=N; j+=i)prime[j] = 0;
}
int main() {int n;sieve_prime();while(cin>>n,n) {if(prime[n]){cout<<n<<" is normal."<<endl;continue;}bool flag = 1;for(int i=2; i<n; i++) {if(pow_mod(i,n,n)!=i) {flag = 0;break;}}if(flag) cout<<"The number "<<n<<" is a Carmichael number."<<endl;elsecout<<n<<" is normal."<<endl;}
}