通过中序排列实现二叉树排序

代码：

class SortTree():
	def __init__(self):
		self.root = None
	def add(self,item):
		node = Node(item)
		cur = self.root
		if self.root == None:
			self.root = node
			return
		while 1:
			#插入节点的值小于根节点的值：往根节点的左侧插
			if node.item < cur.item:
				if cur.left == None:
					cur.left = node
					break
				else:
					cur = cur.left
			else:
				#插入的节点的值大于跟节点：往根节点的右侧插
				if cur.right == None:
					cur.right = node
					break
				else:
					cur = cur.right
def middle(self,root):
	if root == None:
		return
	self.middle(root.left)
	print(root.item)
	self.middle(root.right)

tree = SortTree()
alist = [3,8,5,7,6,2,1]
for i in alist:
    tree.add(i)
tree.middle(tree.root)