杭电 HOJ 1016 Prime Ring Problem 解题报告

    素数环，回溯法，DFS基础题。对于DFS偶还没接触过，看到一篇好的文章，分享下：http://yangjunke111.blog.163.com/blog/static/135279606201041312753102/

    额，直接看代码吧

#include <iostream>
using namespace std;

int n,cas=1,visit[20],result[20]={0,1},p[]={0,0,1,1,0,1,0,1,0,0,0,1,0,1,0,0,0,1,0,1,0,0,0,1,0,0,0,0,0,1,0,1,0,0,0,0,0,1,0,1,0};

void DFS(int num,int pos)
{
    int i;
    if(pos==n&&p[1+result[n]])
    {
        printf("1");
        for(i=2;i<=n;i++)
            printf(" %d",result[i]);
        printf("\n");
        return;
    }
    for(i=2;i<=n;i++)
        if(p[i+num]&&!visit[i])
        {
            result[pos+1]=i;
            visit[i]=1;
            DFS(i,pos+1);
            visit[i]=0;
        }
}

int main()
{
    while(cin>>n)
    {
        memset(visit,0,sizeof(visit));
        printf("Case %d:\n",cas++);
        if(n%2==0)
            DFS(1,1);
        printf("\n");
    }
}