【PAT】1015. Reversible Primes

#define LOCAL #include <iostream> #include <cstdio> #include <cstring> #include <algorithm> #include <string> using namespace std; typedef long long ll; int a[1000100]; bool isprime(int x){ for(int i=2;i*i<=x;i++){ if(x%i==0) return false; } if(x==0 || x==1) return false; else return true; } int main() { #ifdef LOCAL freopen("data.in","r",stdin); freopen("data.out","w",stdout); #endif // LOCAL int n,r; int d[111]={0}; while(scanf("%d",&n)!=EOF){ if(n<0) break; scanf("%d",&r); int len=0; int ans=n; while(n){ d[len++]=n%r; n/=r; } for(int i=0;i<len;i++){ n=n*r+d[i]; } if(isprime(n)&&isprime(ans)) cout<<"Yes"<<endl; else cout<<"No"<<endl; } return 0; }