public static boolean test(HashMap<Integer, List<Integer>> graph, int start, int finish) {
        HashSet<Integer> points = graph.values().stream().flatMap(List::stream).collect(Collectors.toCollection(HashSet::new));
        points.addAll(graph.keySet());
        LinkedList<Integer> queue = new LinkedList<>();
        HashMap<Integer, Boolean> visited = new HashMap<>();

        for (int i = 1; i <= points.size(); i++) {
            visited.put(i, false);
        }
        visited.put(start, true);
        queue.push(start);


        while (!queue.isEmpty()) {
            int current =  queue.pop();
            System.out.print(current + " ");
            List<Integer> neighbours = graph.get(current);
            System.out.println(visited);
            if (neighbours == null) {
                continue;
            }
            for (Integer neighbor : neighbours) {
                if (!visited.get(neighbor)) {
                    queue.add(neighbor);
                    visited.put(neighbor, true);
                }
            }
        }
        return false;
    }

    public static void main(String[] args) {
        HashMap<Integer, List<Integer>> graph = new HashMap<Integer, List<Integer>>();
        graph.put(1, List.of(2, 3, 4));
        graph.put(2, List.of(3, 4, 5));
        graph.put(3, List.of(6));
        test(graph, 2, 1);
    }