hdu 杭电 1016 Prime Ring Problem 果枫

ac代码：

#include<iostream>
using namespace std;

int map[61];
int use[21];
int ss[22];
int n;


void dfs(int i)
{
    if(i==n&&map[ss[i-1]+1]==0)
    {
        for(int l=0;l<n-1;l++)
            cout<<ss[l]<<" ";
        cout<<ss[n-1]<<endl;
    }
    else
    {
        for(int j=2;j<=n;j++)
        {
            if(!use[j]&&map[ss[i-1]+j]==0)
            {
                use[j]=1;
                ss[i]=j;
                i++;
                dfs(i);
                i--;
                use[j]=0;
            }
        }
    }
}
int main()
{

    memset(map,0,sizeof(map));
    int i,j;
    map[0]=map[1]=1;
    for(i=2;i<=30;i++)
    {
        for(j=i*i;j<60;j+=i)
        {
            map[j]=1;
        }
    }
    int num=1;
    while(cin>>n)
    {
        printf("Case %d:\n",num++);
        memset(use,0,sizeof(use));
        ss[0]=1;
        dfs(1);
        cout<<endl;
    }
    return 0;
}