剑指Offer 37 序列化二叉树

请实现两个函数，分别用来序列化和反序列化二叉树
 1 class Solution:
 2     def __init_(self):
 3         self.SerializeStr = ''
 4         
 5     def Serialize(self, root):
 6         if root == None:
 7             return '#'
 8         return str(root.val) + ' ' + self.Serialize(root.left) + ' ' +self.Serialize(root.right)
 9         # write code here
10     def Deserialize(self, s):
11         self.SerializeStr = s
12         return self.DeserializeStr()
13         
14     def DeserializeStr(self):
15         if len(self.SerializeStr) == 0:
16             return None
17         idx = self.SerializeStr.find(' ')
18         node = self.SerializeStr if idx == -1 else self.SerializeStr[:idx]
19         self.SerializeStr = '' if idx == -1 else self.SerializeStr[idx+1:]
20         if node == '#':
21             return None
22         val = int(node)
23         t = TreeNode(val)
24         t.left = self.DeserializeStr()
25         t.right = self.DeserializeStr()
26         return t
27         # write code here