二叉树 类型题

1.前序遍历

def PreOrder(self, root):
	'''打印二叉树(先序)'''
	if root == None:
		return 
	print(root.val, end=' ')
	self.PreOrder(root.left)
	self.PreOrder(root.right)

2.中序遍历

def InOrder(self, root):
	'''中序打印'''
	if root == None:
		return
	self.InOrder(root.left)
	print(root.val, end=' ')
	self.InOrder(root.right)

3.后续遍历

def BacOrder(self, root):
	'''后序打印'''
	if root == None:
		return
	self.BacOrder(root.left)
	self.BacOrder(root.right)
	print(root.val, end=' ')

4.广度遍历

def BFS(self, root):
	'''广度优先'''
	if root == None:
		return
	# queue队列，保存节点
	queue = []
	# res保存节点值，作为结果
	#vals = []
	queue.append(root)

	while queue:
		# 拿出队首节点
		currentNode = queue.pop(0)
		#vals.append(currentNode.val)
		print(currentNode.val, end=' ')
		if currentNode.left:
			queue.append(currentNode.left)
		if currentNode.right:
			queue.append(currentNode.right)
	#return vals

5.深度遍历

def DFS(self, root):
	'''深度优先'''
	if root == None:
		return
	# 栈用来保存未访问节点
	stack = []
	# vals保存节点值，作为结果
	#vals = []
	stack.append(root)

	while stack:
		# 拿出栈顶节点
		currentNode = stack.pop()
		#vals.append(currentNode.val)
		print(currentNode.val, end=' ')
		if currentNode.right:
			stack.append(currentNode.right)
		if currentNode.left:
			stack.append(currentNode.left)			
	#return vals