NYOJ 448 素数环

 1 #include<iostream>
 2 #include<memory.h>
 3 using namespace std;
 4 int n,visit[21],cir[21],pri[40];
 5 void dfs(int k, int n)
 6 {
 7     int i;
 8     if(k == n && pri[1 + cir[n-1]] )
 9     {
10         cout<<1;
11         for(i = 1; i < n; ++i)
12             cout<<" "<<cir[i];
13         cout<<endl;
14     }
15     
16     else
17     {
18         for(i = 2; i <= n; ++i)
19         {
20             if(pri[i + cir[k-1]] && !visit[i])
21             {
22                 visit[i] = 1;
23                 cir[k] = i;
24                 dfs(k+1,n);
25                 visit[i] = 0;
26             }
27         }
28     }    
29 }
30 int main()
31 {
32     pri[2] = 1; pri[3] = 1; pri[5] = 1; pri[7] = 1; pri[11] =1;pri[13] = 1;
33     pri[17] = 1; pri[19] = 1; pri[23] = 1; pri[29] = 1;pri[31] = 1; pri[37] = 1;
34     int i,j,t=0;
35     while(cin>>n,n)
36     {
37         cout<<"Case "<<++t<<":\n";
38         if(n == 1){
39             cout<<1<<endl;
40             continue;
41         }
42         if(n & 1){
43             cout<<"No Answer\n";
44             continue;
45         }
46         memset(visit,0,sizeof(visit));
47         visit[1] = 1; cir[0] = 1;
48         dfs(1,n);
49     }
50     return 0;
51 }