时间限制 400 ms 内存限制 65536 kB 代码长度限制 16000 B 判题程序 Standard 作者 CHEN, Yue 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
#include<cstdio> #include<cmath> bool isprime(int n){ if(n==1||n==0)return false; for(int i=2;i<=sqrt(n);i++){ if(n%i==0)return false; } return true; } int getvs(int n,int r){ int a[100]; int i=0; while(n){ a[i]=n%r; n/=r; i++; } for(int j=0;j<i;j++){ n=n*r+a[j]; } return n; } int main(){ int n,r; scanf("%d",&n); while(n>=0){ if(n==0||n==1){ printf("No\n"); scanf("%d",&n); continue; } scanf("%d",&r); if(isprime(n)){ int x=getvs(n,r); if(isprime(x)){ printf("Yes\n"); }else printf("No\n"); }else printf("No\n"); scanf("%d",&n); } return 0; }