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");

    }

}