树的建立,各种遍历(先根递归,先根非递归,中根递归,中根非递归,后根递归,后根非递归,层次遍历,最近公共祖先的查找,树的删除-tree establishment of various traverse (first - recursive and non - recursive first root, root recursive and non - recursive root, root recursive, non - recursive root level, traverse, the recent public ancestors locate, delete tree