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解题思路：输入一个数n和d。判断n是不是素数，以及n在d进制下，用d进制表示n这个数的反转过来，再转化成十进制，看这个数是不是素数，如果都是素数则打印YES，否则打印No.
#include<iostream> using namespace std; bool isPrime(int num); int reverseNumber(int num, int radix); int main() { int n, d; while(cin>>n) { if(n < 0) break; cin>>d; int rev_n = reverseNumber(n, d); if(isPrime(n) && isPrime(rev_n)) cout<<"Yes"<<endl; else cout<<"No"<<endl; } return 0; } bool isPrime(int num) { if(num < 2) return false; if(num ==2 || num == 3) return true; for(int i = 2; i*i <= num; i ++) if(num % i == 0) return false; return true; } int reverseNumber(int num, int radix) { int rev_num = 0; while(num != 0) { rev_num *= radix; rev_num += num % radix; num /= radix; } return rev_num; }