Python实现二叉树的遍历

class BinaryTree(object):
def __init__(self, value=None, left=None, right=None):
self.value = value
self.left = left
self.right = right

def rebuild(self, preOrder, inOrder):
"""
根据前序列表和中序列表,重建二叉树
:param preOrder: 前序列表
:param inOrder: 中序列表
:return: 二叉树
"""
if preOrder == None or inOrder == None or len(preOrder) <=0 or len(inOrder) <=0 \
or len(preOrder) != len(inOrder):
return None
cur = BinaryTree(preOrder[0])
index = inOrder.index(preOrder[0])
cur.left = self.rebuild(preOrder[1: index+1], inOrder[:index])
cur.right = self.rebuild(preOrder[index+1:], inOrder[index+1:])
return cur

def preOrder(self, tree):
"""
前序遍历
:param tree:
:return:
"""
if tree == None:
return None
print(tree.value, end=' ')
self.preOrder(tree.left)
self.preOrder(tree.right)

def preOrderLoop(self, tree):
"""
前序遍历的循环实现
:param tree:
:return:
"""
if tree == None:
return None
lst = []
node = tree
while node != None or len(lst) > 0:
if node != None:
lst.append(node)
print(node.value, end=' ')
node = node.left
else:
item = lst[len(lst)-1]
lst = lst[:-1]
node = item.right

def inOrder(self, tree):
"""
中序遍历
:param tree:
:return:
"""
if tree == None:
return None
self.inOrder(tree.left)
print(tree.value, end=' ')
self.inOrder(tree.right)

def inOrderLoop(self, tree):
"""
中序遍历循环实现
:param tree:
:return:
"""
if tree == None:
return
lst = []
node = tree

while node != None or len(lst) > 0:
if node != None:
lst.append(node)
node = node.left
else:
item = lst[len(lst)-1]
lst = lst[:-1]
print(item.value, end=' ')
node = item.right

def postOrder(self, tree):
"""
后序遍历
:param tree:
:return:
"""
if tree == None:
return None
self.postOrder(tree.left)
self.postOrder(tree.right)
print(tree.value, end=' ')

def postOrderLoop(self, tree):
"""
后续遍历的循环实现
:param tree:
:return:
"""
if tree == None:
return None

visited = set()
lst = []
node = tree

while node != None or len(lst) > 0:
if node != None:
lst.append(node)
node = node.left
else:
item = lst[len(lst)-1]
if item.right != None and item.right not in visited:
node = item.right
else:
print(item.value, end=' ')
visited.add(item)
lst = lst[:-1]