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：