1015. Reversible Primes (20)

时间：2015-01-30 07:52:34 阅读：145 评论：0 收藏：0 [点我收藏+]

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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

 1 #include <iostream>
 2 #include <algorithm>
 3 using namespace std;
 4  
 5  
 6 bool cha(int n)
 7 {
 8 if(n==1)  return false;//注意1不是素数
 9 bool temp=true;
10     for(int i=2;i<n;i++)
11 if(n%i==0)
12 {
13    temp=false;
14    break;
15 }
16  
17 return temp;
18 }
19  
20 int shu[101];
21  
22  
23 int zhuan(int n,int d)
24 {
25 int count=0;
26 int tem=n;
27      while(tem)
28  {
29    shu[count++]=tem%d;
30    tem=tem/d;
31  }
32      
33  tem=0;
34  int j;
35      for( j=0;j<count-1;j++)
36  tem=(tem+shu[j])*d;
37  tem+=shu[j];
38  return tem;
39  
40 }
41  
42  
43  
44 int main()
45 {
46    int n;
47    while(cin>>n)
48    {
49    if(n<0)  break;
50    
51   int d;
52       cin>>d;
53       bool ifis=cha(n);
54   if(!ifis)  cout<<"No"<<endl;
55   else
56   {
57       int rev=zhuan(n,d);
58   ifis=cha(rev);
59           if(!ifis)  cout<<"No"<<endl;
60   else   cout<<"Yes"<<endl;
61   }
62  
63    }
64    return 0;
65 }
66