1 #include <iostream>
2 #include <cstdio>
3 #include <cstring>
4 #include <cstdlib>
5 #include <algorithm>
6 #include <vector>
7 #define sc(x) scanf("%d",&(x))
8 #define sc2(x,y) scanf("%d%d", &(x), &(y))
9 #define pn printf("%\n")
10 #define PF(x) printf("%d ",x)
11 #define pf(x) printf("%d\n",x)
12 #define CL(x, y) memset(x, y, sizeof(x))
13 #define FOR(i,b,e) for(int i = b; i <= e; i++)
14 #define max(a, b) (a > b ? a : b)
15 #define ABS(a, b) (a > b ? a - b : b - a)
16 using namespace std;
17 const int MAX = 25;
18 int ans[MAX], used[MAX], n, N = 0;
19 void show();
20 void DFS(int pos);
21 int main()
22 {
23 sc(n);
24 CL(used, 0);
25 DFS(0);
26 cout << "种类为：" << N << endl;
27 return 0;
28 }
29 void DFS(int pos)
30 {
31 if(pos == n)
32 {
33 show();
34 N++;
35 return ;
36 }
37 used[pos] = 0;
38 DFS(pos+1);
39 used[pos] = 1;
40 DFS(pos+1);
41 }
42 void show()
43 {
44 int k = 0;
45 FOR(j,0,n-1)
46 // PF(used[j]);
47 if(used[j])
48 {
49 PF(j+1);
50 k++;
51 }
52 if(!k)printf("空集");
53 cout << endl;
54 }
