nCk 조합 모두 참조하기

inline int ctz(int a) {
    int r = 0;
    while (!(a % 2)) a >>= 1, r++;
    return r;
}
 
int main() {
    int p = (1 << k) - 1;
    int maxp = (1 << n) - 1;
    while (p <= maxp) {
        int t = p | (p - 1);
        p = (t + 1) | (((~t & -~t) - 1) >> (ctz(p) + 1));
    }
}