Function rec

code/data-structures/dancing_links.test.cpp:5–17

vi cur;

void rec(dancing_links<int> &left) {
  if (left.front == NULL) {
    perms.push_back(vi(cur));
  } else {
    for (dancing_links<int>::node *it = left.front; it; it = it->r) {
      cur.push_back(it->item);
      left.erase(it);
      rec(left);
      left.restore(it);
      cur.pop_back();
    }
  }
}

void test() {
  int N = 8;