@Test
    public void testSample2() throws Exception {
        String[] strs = {"hot", "dot", "dog", "lot", "log"};
        Set<String> set = new HashSet<String>();
        Collections.addAll(set, strs);
        List<List<String>> list = wordLadderII.findLadders("hit", "cog", set);
        Utils.printStringStringList(list);
    }