code: private List<Word>[] toWords(List<Node> leaf){
          List<Word>[] result = new ArrayList[leaf.size()];
          int i = 0;
          if(LOGGER.isDebugEnabled()) {
              LOGGER.debug("全切分结果：");
          }
          for(Node node : leaf){
              result[i++] = toWords(node);
              if(LOGGER.isDebugEnabled()) {
                  LOGGER.debug("\t" + i + "：" + result[i - 1]);
              }
          }
          return result;
      }
docs: 从树叶开始反向遍历生成全切分结果
  @param leaf 树叶节点集合
  @return 全切分结果集合