【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;}