PAT 甲级【1015 Reversible Primes】

1. 考察素数判断
2. 考察进制转换

import java.io.IOException;
import java.io.InputStreamReader;
import java.io.StreamTokenizer;

public class Main {
    @SuppressWarnings("uncheck")
    public static void main(String[] args) throws IOException {
        StreamTokenizer st = new StreamTokenizer(new InputStreamReader(System.in));
        int n, d;
        while (true) {
            st.nextToken();
            n = (int) st.nval;
            if (n < 0) {
                break;
            }
            st.nextToken();
            d = (int) st.nval;
            String str = Integer.toString(n, d);
            String reversestr = new StringBuilder(str).reverse().toString();

            int p2 = Integer.parseInt(reversestr, d);

            if( isPrime(n) && isPrime(p2)){
                System.out.println("Yes");
            }else{
                System.out.println("No");
            }
        }
    }

    public static boolean isPrime(int n) {
        if (n == 1) {
            return false;
        }
        for (int i = 2; i <= Math.sqrt(n); i++) {
            if (n % i == 0) {
                return false;
            }
        }
        return true;
    }
}