很多人都使用“父—子结构＋递归算法”来显示树型的层次结构，这里给介绍一种简单方便的数据结构和算法，快速显示树型的层次结构-many people use a "parent-child structure + recursive algorithm" to show the level of tree structure, here introduced to a simple data structure and algorithm, shows the hierarchical structure tree