用python实现排序二叉树（中序）_python对树进行中序排序

class SortTree():
 
    def __init__(self):
        self.root = None
 
    def add(self, item):
        node = Node(item)
 
        cur = self.root
 
        if cur == None:
            self.root = node
            return
 
        while cur:
 
            if item > cur.item:
 
                if cur.right == None:
                    cur.right = node
                    break
                else:
                    cur = cur.right
 
            else:
 
                if cur.left == None:
                    cur.left = node
                    break
                else:
                    cur = cur.left
 
    def travle(self):
 
        cur = self.root
 
        q = [cur]
        while q:
            nd = q.pop(0)
            print(nd.item)
            if nd.left:
                q.append(nd.left)
 
            if nd.right:
                q.append(nd.right)
    def middle(self, root):
 
        if root == None:
            return
 
        self.middle(root.left)
        print(root.item)
        self.middle(root.right)
 
 
 
t = SortTree()
 
alist = [3, 8, 5, 7, 6, 2, 9, 4, 1]
 
for i in alist:
    t.add(i)
 
# t.travle()
t.middle(t.root)