hdoj 1016经典问题素数环

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//经典搜索题 #include <iostream>#include <cstring>using namespace std;int primelist[38] = {0,0,1,1,0,1,0,1,0,0,0,1,0,1,0,0,0,1,0,1,0,0,0,1,0,0,0,0,0,1,0,1,0,0,0,0,0,1};//素数表， int n;int A[21];   //存放序列结果 int vis[21];//访问标记 void DFS(int cur){     if(cur == n && primelist[A[n-1]+A[0]])    //结束条件      {            cout<<A[0];            for(int i = 1; i < n; ++i)            {                    cout<<" "<<A[i];                   }            cout<<endl;     }     else     {            for(int i = 2; i <= n;++i)            {                    if(!vis[i] && primelist[i + A[cur-1]])   //如果i没有用过并且能与前面的数和成素数                     {                              A[cur] = i;    //标记i已访问                               vis[i] = 1;    //将i加入结果序列                               DFS(cur+1);    //递归访问                               vis[i] = 0;    //回溯法标准框架去掉标记                     }            }     }}int main(){    int count = 0;    A[0] = 1;    while(cin>>n)    {          memset(vis,0,sizeof(vis));          count++;          cout<<"Case "<<count<<":"<<endl;          DFS(1);          cout<<endl;    }    return 0;}

刘汝佳白书上的题目，回溯法标准框架