输入一个字符串，并建成一棵二叉树，满足左子树的字符都要小于根结点的字符，右字树的字符都要大于根结点的字符，每个结点值有字符和字符的出现次数，并用三种遍历方法打印，比较是否与自己想象的相一致。再求树的深度、叶子结点数、最大结点值。-Enter a string, and the completion of a binary tree, to meet the characters in the left subtree must be less than the root node of the