1015 Reversible Primes （20 分）(简单题)

1015 Reversible Primes （20 分）(简单题)

A reversible prime in any number system is a prime whose “reverse” in that number system is also a prime. For example in the decimal system 73 is a reversible prime because its reverse 37 is also a prime.

Now given any two positive integers N (<10^​5​​ ) and D (1<D≤10), you are supposed to tell if N is a reversible prime with radix D.

Input Specification:

The input file consists of several test cases. Each case occupies a line which contains two integers N and D. The input is finished by a negative N.

Output Specification:

For each test case, print in one line Yes if N is a reversible prime with radix D, or No if not.

Sample Input:

73 10
23 2
23 10
-2

Sample Output:

Yes
Yes
No

#include <iostream>
using namespace std;
bool isPrime(int a){
    if(a==0||a==1) return false;
    for(int i=2;i*i<=a;i++){
        if(a%i==0) return false;
    }
    return true;
}
int main(){
    while(1){
        int n,tmp,m,sum=0;
        cin>>n;
        if(n<0) break;
        cin>>m;
        tmp=n;
        while(tmp){
            sum = sum*m + (tmp%m);
            tmp/=m;
        }
        printf("%s\n",isPrime(n)&&isPrime(sum)?"Yes":"No");
    }
    return 0;
}