python 二叉树

定义：

class BTree(object):
def init(self, value):
self.l_child = None
self.r_child = None
self.value = value
def insert_left(self, value):
bt_node = BTree(value)
bt_node.l_child = self.l_child
self.l_child = bt_node
def insert_right(self, value):
bt_node = BTree(value)
bt_node.r_child = self.r_child
self.r_child = bt_node

def in_order(node, return_list):
if node:
in_order(node.l_child, return_list)
return_list.append(node.value)
in_order(node.r_child, return_list)
return return_list

插入节点

n0 = BTree(0)
n0.insert_left(1)
n0.insert_right(2)
n0.l_child.insert_left(3)
n0.l_child.insert_right(4)
n0.r_child.insert_left(5)
n0.r_child.insert_right(6)

树为：

0
1 2
3 4 5 6

调用中序遍历

>>> in_order(n0,[])
[3, 1, 4, 0, 5, 2, 6]

前序遍历

def pre_order(node, return_list):
if node:
return_list.append(node.value)
pre_order(node.l_child, return_list)
pre_order(node.r_child, return_list)
return return_list

>>> pre_order(n0,[])
[0, 1, 3, 4, 2, 5, 6]

后序遍历

def post_order(node, return_list):
if node:
post_order(node.l_child, return_list)
post_order(node.r_child, return_list)
return_list.append(node.value)
return return_list

>>> post_order(n0,[])
[3, 4, 1, 5, 6, 2, 0]