python创建中序二叉树并按照中序print

使用python创建二叉树

实现：

1. 如果二叉树为空，则创建二叉树实例
2. 如果当前结点为空，则创建结点。否则判断：
   
   • 如果输入值小于当前结点值，则添加到左结点
   • 如果输入值大于或等于当前值，则添加到右结点

代码

#!/usr/bin/env python3# -*- coding: utf-8 -*-class Node(object):        """docstring for Node"""        def __init__(self, arg):                super(Node, self).__init__()                self.val = arg                self.left = None                self.right = Noneclass Tree(object):        """docstring for Tree"""        def __init__(self):                super(Tree, self).__init__()                self.root = None        def init_tree(self, val, node=None):                if node is None:                        node = self.root                if self.root is None:                        self.root = Node(val)                else:                        if val < node.val:                                if node.left is not None:                                        self.init_tree(val, node.left)                                else:                                        node.left = Node(val)                        else:                                if node.right is not None:                                        self.init_tree(val, node.right)                                else:                                        node.right = Node(val)        def print_tree(self):                """docstring for print_tree"""                if self.root is not None:                        self.print_tree_node(self.root)                else:                        print("it's an empty tree")        def print_tree_node(self, node):                """docstring for print_tree"""                if node is not None:                        self.print_tree_node(node.left)                        print(node.val)                        self.print_tree_node(node.right)if __name__ == '__main__':        tree = Tree()        #  print(tree)        tree.init_tree(3)        tree.init_tree(4)        tree.init_tree(7)        tree.init_tree(5)        tree.init_tree(1)        tree.print_tree()

运行结果

参考：
http://stackoverflow.com/questions/2598437/how-to-implement-a-binary-tree-in-python