二叉树是采用递归定义的，实现起来代码简洁并且它在具体的计算机科学中有很重要的运用，是一种很重要的数据结构，二叉树有三种遍历和建立的方式。-Binary Tree is a recursive definition, the code is simple to implement and it has very important applications in computer science in particular, is a very important data structure,