三种方法生成子集

#include <bits/stdc++.h>
#define _for(i,a,b) for(int i = (a);i < (b);i ++)
using namespace std;

vector<vector<int>> rnt;
void print_subset1(vector<int> A,vector<int> B)
{
    vector<int> tmp;
    _for(i,0,A.size())
        tmp.push_back(B[A[i]]);
    rnt.push_back(tmp);
    
    int s = A.size() ? A[A.size()-1]+1 : 0;
    _for(i,s,B.size())
    {
        A.push_back(i);
        print_subset1(A,B);
        A.pop_back();
    } 
}

void print_subset2(vector<int> A,vector<int> B)
{
    if(A.size()==B.size())
    {
        vector<int> tmp;
        _for(i,0,A.size())
            if(A[i]) tmp.push_back(B[i]);
        rnt.push_back(tmp);
        return ;
    }
    A.push_back(1); print_subset2(A,B);
    A.pop_back(); A.push_back(0);print_subset2(A,B);
}

void _print_subset3(vector<int> B,int s)
{
    vector<int> tmp;
    _for(i,0,B.size())
        if(s&(1<<i)) tmp.push_back(B[i]);
    rnt.push_back(tmp); 
}

void print_subset3(vector<int> B)
{
    _for(i,0,1<<B.size())
        _print_subset3(B,i);
}

void print_rnt()
{
    _for(i,0,rnt.size())
    {
        _for(j,0,rnt[i].size())
        {
            cout << rnt[i][j] << " ";
        }
        cout << endl;
    }
    cout << endl;
}
int main()
{
    vector<int> A;
    vector<int> B {1,3,9};
    
    
    cout << "Incremental Construction:" << endl; 
    print_subset1(A,B);
    print_rnt();
    rnt.clear();
    
    
    cout << "Bit Vector" << endl;
    print_subset2(A,B);
    print_rnt();
    rnt.clear();
    
    
    cout << "Binary System" << endl;
    print_subset3(B);
    print_rnt();
    rnt.clear();
    
    
    return 0;
}