1015. Reversible Primes
1015. Reversible Primes (20)
时间限制
400 ms
内存限制
32000 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 -2Sample Output:
Yes Yes No
1 #include <iostream>
2 #include <fstream>
3 #include <vector>
4 #include <string>
5 #include <algorithm>
6 #include <map>
7 #include <stack>
8 #include <cmath>
9 #include <queue>
10 #include <set>
11
12
13 using namespace std;
14
15
16
17 bool isPrime( int x )
18 {
19 if( x < 2 )
20 {
21 return false;
22 }
23 else if( x == 2 || x == 3 )
24 {
25 return true;
26 }
27 else if( x%2 == 0 )
28 {
29 return false;
30 }
31 else
32 {
33
34 for( int i = 2 ; i * i <= x ; ++i )
35 {
36 if( x % i == 0 )
37 {
38 return false;
39 }
40 }
41
42 return true;
43 }
44 }
45
46
47
48 int main()
49 {
50
51
52
53 int N;
54 int D;
55
56 while( cin >> N )
57 {
58 if( N < 0 )
59 {
60 break;
61 }
62 else
63 {
64 cin >> D;
65
66 if( isPrime(N) )
67 {
68
69 int n = N;
70
71 queue<int> queue;
72
73
74 while( n != 0 )
75 {
76 queue.push(n%D);
77 n = n / D;
78 }
79
80 int reverse = 0;
81
82 while(!queue.empty())
83 {
84 reverse*= D;
85 reverse += queue.front();
86 queue.pop();
87 }
88
89 if( isPrime( reverse ) )
90 {
91 cout << "Yes" << endl;
92 }
93 else
94 {
95 cout << "No" << endl;
96 }
97
98 }
99 else
100 {
101 cout << "No" << endl;
102 }
103
104
105
106 }
107 }
108
109
110
111
112 return 0;
113 }
