python二叉树递归算法之后序遍历，前序遍历，中序遍历

 #!/usr/bin/env python

 # -*- coding: utf-8 -*-

 # @Date    : 2016-11-18 08:53:45

 # @Author  : why_not_try

 # @Link    : http://example.org

 # @Version : python 2.7

 class Tree(object):

     def __init__(self,data,left,right):

         self.data=data

         self.left=left

         self.right=right

 def post_visit(Tree):

     if Tree:

         post_visit(Tree.left)

         post_visit(Tree.right)

         print Tree.data

 def pre_visit(Tree):

     if Tree:

         print Tree.data

         pre_visit(Tree.left)

         pre_visit(Tree.right)

 def in_visit(Tree):

     if Tree:

         in_visit(Tree.left)

         print Tree.data

         in_visit(Tree.right)

 node1=Tree(1,0,0)

 node2=Tree(2,0,0)

 node3=Tree(3,node1,node2)

 node4=Tree(4,0,0)

 node5=Tree(5,node4,node3)

 print "the post_visit is ....."

 post_visit(node5)

 print "the pre_visit is......."

 pre_visit(node5)

 print "the in_visit is ......."

 in_visit(node5)

代码很简单，相信一看大部分就能理解。在每一个遍历算法中首先if Tree 为了防止树的左节点或右节点为空时（0代表为空）还去遍历 ，此时程序运行将会报错。

此为node5:

运行结果如下：