gospers_hack.cpp

#include <bits/stdc++.h> 

using namespace std; 

void print_set(int s) {
    printf("%d: ", s);
    
    for(int i = 1; 0 < s; i++) {
        if((s & 1) == 1) {
            printf("%d, ", i);
        }
        
        s = s >> 1;
    }
    
    printf("\n");
}

void gospers_hack(int k, int n) {
    int set = (1 << k) - 1;
    int limit = (1 << n);

    while(set < limit) {
        print_set(set);
        
        int c = set & - set;
        int r = set + c;
        set = (((r ^ set) >> 2) / c) | r;
    }
}


int main() {
    // set of size 4, with limit of 2^5
    gospers_hack(4, 5);
    
    return 0; 
}