HDU 1016Prime Ring Problem

標籤：bsp   namespace   nbsp   cin   main   ace   color   count   style   

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

題意：輸入一個數，給出符合要求的素數環。

經典的dfs遍曆。

 1 #include<iostream> 2 #include<cstring> 3 #include<cmath> 4 using namespace std; 5  6 int visited[25]; 7 int pos[25]; 8 int n, kase = 0; 9 10 int judge(int x)                 //判斷是否為素數11 {12     for (int i = 2; i <= sqrt(x); i++)13     {14         if (x%i == 0)     return 0;15     }16     return 1;17 }18 19 void dfs(int x,int count)20 {21     pos[count] = x;22     visited[x] = 1;23     if (count == n && judge(x + pos[1]))24     {25         for (int i = 1; i < n; i++)26             cout << pos[i] << " ";27         cout << pos[n];28         cout << endl;29     }30     for (int k = 2; k <= n; k++)31     {32         if (!visited[k] && judge(k+pos[count]))33         {34             dfs(k, count+1);35             visited[k] = 0;36         }37     }38 }39 40 int main()41 {42     while (cin >> n && n)43     {44         memset(visited, 0, sizeof(visited));45         memset(pos, 0, sizeof(pos));46         kase++;47         cout << "Case " << kase << ":" << endl;48         dfs(1,1);49         cout << endl;50     }51     return 0;52 }

 

HDU 1016Prime Ring Problem