hdoj1016(简单DFS)

#include <stdio.h>
#include <string.h>
#include <iostream>
using namespace std;
int isprime[40]={0,0,1,1,0,1,0,1,0,0,0,1,0,1,0,0,0,1,0,1,0,0,0,1,0,0,0,0,0,1,0,1,0,0,0,0,0,1,0,0};
int vis[21];//用来记录是否被访问过
int a[21];//用来记录位置顺序
int n;
void dfs(int num)
{
int i;
if(num==n&&(isprime[a[n-1]+a[0]])){
cout<<a[0];
for(i=1;i<n;i++)
{
cout<<" "<<a[i];
}
cout<<endl;
}else{
for(i=2;i<=n;i++)
{
if(vis[i]==0&&isprime[i+a[num-1]])
{
vis[i]=1;
a[num++]=i;
dfs(num);
vis[i]=0;
num--;
}
}
}
}
int main()
{
a[0]=1;
int k=1;
while(scanf("%d",&n)!=EOF)
{
cout<<"Case "<<k++<<":"<<endl;
dfs(1);
cout<<endl;
}
return 0;
}