（1）分别采用递归和非递归算法建立二叉树； （2）采用先序、中序和后序三种方式遍历该二叉树； （3）按层次遍历该二叉树。 -(1) were used to establish the recursive and non-recursive algorithm for binary tree (2) using first-order, middle order and post-order traversal of the binary tree in three ways (