序列化二叉树

题目描述
请实现两个函数，分别用来序列化和反序列化二叉树

# -*- coding:utf-8 -*-
class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None
        
class Solution:
    
    def Serialize(self, root):
        # write code here
        ss = ['']
        def dfs(p):
            if not p: 
                ss[0]+='-#'
                return
            ss[0]+=('-'+str(p.val))
            dfs(p.left)
            dfs(p.right)
        dfs(root)
        return ss[0]
        
    def Deserialize(self, s):
        # write code here
        ss = s[1:].split('-')
        i = [-1]
        def dfs():
            i[0]+=1
            if ss[i[0]]=='#':  return None
            root = TreeNode(int(ss[i[0]]))
            root.left = dfs()
            root.right = dfs()
            return root
        return dfs()