1015 Reversible Primes

个人学习记录，代码难免不尽人意。

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 (<10 5) 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

#include
#include
#include
#include
#include
#include
using namespace std;
bool isprime(int num){
	if(num<=1) return false;
	
		int n=(int)sqrt(num*1.0);
		for(int i=2;i<=n;i++){
			if(num%i==0) return false;
		}
		return true;
	
	
}
int changeandreverse(int n,int radix){
	int m=0;
	while(n!=0){
		m=m*radix+(n%radix);
		n/=radix;
	}
	return m;
}
int main(){
  int n,radix;
  scanf("%d",&n);
  while(n>=0){
  	scanf("%d",&radix);
  	int re_n=changeandreverse(n,radix);
  	if(isprime(n)&&isprime(re_n)) printf("Yes\n");
  	
  	else printf("No\n");
  	 scanf("%d",&n);
  }
  return 0;
}

本题重点掌握判断素数的方法以及sprt函数只能对浮点数进行运算。