A1015 Reversible Primes 反转数字后仍为素数

1015 Reversible Primes 分数 20

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.

任何数字系统中的可逆素数都是其在该数字系统中“逆”也是素数的素数。例如，在十进制中，73是可逆素数，因为它的逆37也是素数。

现在给定任意两个正整数N（＜10^5）和D（1＜D≤10），你应该判断N是否是以D为基数的可逆素数。

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.

输入文件由几个测试用例组成。每种情况都占据一行，其中包含两个整数N和D。输入以负N结束。

Output Specification:

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

对于每个测试用例，如果N是以D为基数的可逆素数，则打印一行“是”，如果不是，则打印“否”

Sample Input:

73 10
23 2
23 10
-2

Sample Output:

Yes
Yes
No

#include
#include
using namespace std;//判断是否为素数bool isprime(int a){if(a<=1)return false;for(int i=2;i<(int)sqrt(1.0*a);i++){if(a%i==0) return false;}return true;
}int a[100001];
int main()
{while(1){int n,d;cin>>n>>d;if(n<0)break;if(isprime(n)==false)cout<<"No"<