DFS_子集

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <algorithm>
#include <vector>
#define sc(x) scanf("%d",&(x))
#define sc2(x,y) scanf("%d%d", &(x), &(y))
#define pn printf("%
")
#define PF(x) printf("%d ",x)
#define pf(x) printf("%d
",x)
#define CL(x, y) memset(x, y, sizeof(x))
#define FOR(i,b,e)  for(int i = b; i <= e; i++)
#define max(a, b) (a > b ? a : b)
#define ABS(a, b) (a > b ? a - b : b - a)
using namespace std;
const int MAX = 25;
int ans[MAX], used[MAX], n, N = 0;
void show();
void DFS(int pos);
int main()
{
    sc(n);
    CL(used, 0);
    DFS(0);
    cout << "种类为：" << N << endl;
    return 0;
}
void DFS(int pos)
{
    if(pos == n)
    {
        show();
        N++;
        return ;
    }
    used[pos] = 0;
    DFS(pos+1);
    used[pos] = 1;
    DFS(pos+1);
}
void show()
{
    int k = 0;
    FOR(j,0,n-1)
//    PF(used[j]);
    if(used[j])
    {
        PF(j+1);
        k++;
    }
    if(!k)printf("空集");
    cout << endl;
}