public boolean canVisitAllRooms(List<List<Integer>> rooms) {
        if (rooms == null || rooms.size() <= 1)
            return true;
        Set<Integer> set = new HashSet<>();
        go(rooms, set, 0);
        return set.size() == rooms.size();
    }
Why Did you create this class? what does it do?
src/problems/medium/RoomsAndKeys.java