这题目什么意思。。。
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 10
23 2
23 10
-2
Sample Output:
Yes
Yes
No
AC代码
#include<iostream>
#include<cstdio>
#include<memory.h>
#include<algorithm>
#include<cstring>
#include<queue>
#include<cmath>
#include<vector>
#include<cstdlib>
#include<cmath>
#include<iomanip>
#include<string>
using namespace std;
#define MAX 0x6fffffff
bool isprime(int n){
if(n==1)
return false;
int q = sqrt(n+0.0);
for(int i=2;i<=q;++i){
if(n%i==0)
return false;
}
return true;
}
int reverse(int n, int radix){
int ans = 0;
while(n>0){
ans = ans*radix + n%radix;
n /= radix;
}
return ans;
}
int main(){
//freopen("in.txt", "r", stdin);
int n, d;
while(cin>>n, n>=0){
cin>>d;
if(isprime(n) && isprime(reverse(n, d)))
printf("Yes\n");
else
printf("No\n");
}
// fclose(stdin);
return 0;
}
