1015. Reversible Primes (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.

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 1023 223 10-2

Sample Output:

YesYesNo

#include <iostream>#include <string>#include <cmath>using namespace std;bool isprime(int n){    if(n==1)        return false;    for(int i=2; i<=sqrt(n); i++)    {        if(n%i == 0)            return false;    }    return true;}int trans(int n, int radix){    int res = 0, i = 0;    int temp[1000];    while(n)    {        temp[i++] = n%radix;        n /= radix;    }    for(int j=0; j<i; j++)    {        res *= radix;        res += temp[j];    }    return res;}int main(){    int temp, radix;    int n;    while(cin >> n && n >= 0)    {        cin >> radix;        if(isprime(n) && isprime(trans(n, radix)))            cout << "Yes" << endl;        else            cout << "No" << endl;    }}