[PAT] 1015 Reversible Primes (20 分)Java
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 (<105) 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
1 import java.io.BufferedReader; 2 import java.io.IOException; 3 import java.io.InputStreamReader; 4 5 /** 6 * @Auther: Xingzheng Wang 7 * @Date: 2019/2/20 22:41 8 * @Description: pattest 9 * @Version: 1.0 10 */ 11 public class PAT1015 { 12 13 public static void main(String[] args) throws IOException { 14 BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); 15 while (true) { 16 String[] in = reader.readLine().split(" "); 17 int num = Integer.parseInt(in[0]); 18 if (num < 0) break; 19 int indax = Integer.parseInt(in[1]); 20 if (isprime(num) && isprime(reve(num,indax))) { 21 System.out.println("Yes"); 22 }else{ 23 System.out.println("No"); 24 } 25 } 26 } 27 28 private static int reve(int num, int indax) { 29 StringBuilder sb = new StringBuilder(Integer.toString(num, indax)).reverse(); 30 return Integer.parseInt(sb.toString(), indax); 31 } 32 33 private static boolean isprime(int num){ 34 if(num == 1) return false; 35 for (int i = 2; i <= Math.sqrt(num); i++) { 36 if (num % i == 0) 37 return false; 38 } 39 return true; 40 } 41 }