PAT 1015 Reversible Primes

1015. Reversible Primes (20)

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 <iostream>
#include <string.h>
#include <stdlib.h>
#include <algorithm>
#include <math.h>
#include <stdio.h>
#include <queue>

using namespace std;
int n,d;
int bin[105];
bool judge(int x)
{
  if(x==1||x==0) return false;
  if(x==2) return true;
  for(int i=2;i*i<=x;i++)
  {
    if(x%i==0)
      return false;
  }
  return true;
}
void fun(int x,int d)
{
  int cnt=0;
  while(x>=d)
  {
    bin[cnt++]=x%d;
    x/=d;
  }
  if(x>0)
    bin[cnt++]=x;
  int num=0;
  for(int i=0;i<cnt;i++)
  {
    num*=d;
    num+=bin[i];
  }
  if(!judge(num))
    printf("No
");
  else
    printf("Yes
");
}
int main()
{
  while(scanf("%d",&n)!=EOF)
  {
    if(n<0)
      break;
    scanf("%d",&d);
    if(!judge(n))
    {
      printf("No
");
      continue;
      
    }
    fun(n,d);
  }
  return 0;

}