A1015 Reversible Primes (20 分)PAT甲级真题（C++）满分题解【进制转换+素数判断】

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

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

代码如下：

#include
#include
using namespace std;
bool isprime(int n)
{
    if(n<=1)return false;
    int mid=int(sqrt(n));
    for(int i=2;i<=mid;i++)
    {
        if(n%i==0)
            return false;
    }
    return true;
}
int main()
{
    int n,d;
    while(true)
    {
        scanf("%d",&n);
        if(n<0)
            break;
        scanf("%d",&d);
        if(!isprime(n)){
            printf("%sn","No");
            continue;
        }
        int index=0,convert[100000];
        do{
            convert[index++]=n%d;
            n=n/d;
        }while(n!=0);
        int reverse=0;
        for(int i=0;i 
运行结果如下：