二叉树的建立与遍历.中序建立一棵二叉树，每个结点的数据域数据为char型，并按三种方式遍历（前序，中序，后序）。输出遍历结果。-The establishment and tree traversal. In order to establish a binary tree, each node of the data field for the char data type, and three ways traversal (pre-order, in sequence, after the