HDU 1016Prime Ring Problem

http://acm.hdu.edu.cn/showproblem.php?pid=1016

题意：输入一个数，给出符合要求的素数环。

经典的dfs遍历。

 #include<iostream>
 #include<cstring>
 #include<cmath>
 using namespace std;

 int visited[];
 int pos[];
 int n, kase = ;

 int judge(int x)                 //判断是否为素数
 {
     for (int i = ; i <= sqrt(x); i++)
     {
         if (x%i == )     return ;
     }
     return ;
 }

 void dfs(int x,int count)
 {
     pos[count] = x;
     visited[x] = ;
     if (count == n && judge(x + pos[]))
     {
         for (int i = ; i < n; i++)
             cout << pos[i] << " ";
         cout << pos[n];
         cout << endl;
     }
     for (int k = ; k <= n; k++)
     {
         if (!visited[k] && judge(k+pos[count]))
         {
             dfs(k, count+);
             visited[k] = ;
         }
     }
 }

 int main()
 {
     while (cin >> n && n)
     {
         memset(visited, , sizeof(visited));
         memset(pos, , sizeof(pos));
         kase++;
         cout << "Case " << kase << ":" << endl;
         dfs(,);
         cout << endl;
     }
     return ;
 }