浙江大学PAT_甲级_1015. Reversible Primes (20)

题目链接：点击打开链接

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

我的Java代码：

import java.util.*;
import java.math.*;
import static java.lang.System.*;
public class Main
{
	public boolean IsPrime(int value)//判断素数方法  
    {
        int i = 2;    
        if (value == 0 || value == 1)    
            return false;    
        for (i=2; i <=Math.sqrt(value); i++)    
        {
            if (value%i == 0)    
                return false;  
        }
        return true;  
    }
	public int reverse(int num,int d)//将10进制数字转换为d进制,并翻转,再转换为10进制
	{
		int sum=0;
		do
		{
			sum=sum*d+num%d;
			num=num/d;
		}while(num!=0);
		return sum;
	}
	public static void main(String[] args)
	{
		Scanner cin=new Scanner(in);
		Main m=new Main();
		int num=0,d=1;//num输入的数字,d进制
		while(cin.hasNextInt())
		{
			num=cin.nextInt();
			if(num<0)//输入负数结束
				break;
			d=cin.nextInt();
			if(m.IsPrime(num)&&m.IsPrime(m.reverse(num, d)))//num是质数,且翻转后还是质数
			{
					out.println("Yes");
			}
			else
			{
				out.println("No");
			}
		}
	}
}