combi pe bits

#include <bits/stdc++.h>
using namespace std;
#define MAXBITS 32

int main()
{
    int n, k;
    cin >> n >> k;
    assert(n >= k && n <= 10);
    int b = 1 << n;
    for (int a = 0; a < b; a++)
    {
        cerr << "nr: " << a << ' ';
        cerr << "bits(rev): ";
        for (int i = 0; i < MAXBITS; i++)
            cerr << bool(a & (1 << i));//repr e inversa
        cerr << "poz: ";
        for (int i = 0; i < MAXBITS; i++)
            if (a & (1 << i))
                cerr << i << ' ';
        //comb
        cerr << "comb: ";
        int cnt = 0;
        for (int i = 0; i < MAXBITS; i++)
            if (a & (1 << i))
                cnt++;
        if (cnt == k)
            for (int i = 0; i < MAXBITS; i++)
                if (a & (1 << i))
                    cerr << i << ' ';
        cerr << endl;
    }
    return 0;
}