leetcode:Serialize and Deserialize Binary Tree

Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment.

Design an algorithm to serialize and deserialize a binary tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized
to the original tree structure.

For example, you may serialize the following tree

1
/ \
2   3
/ \
4   5

as

"[1,2,3,null,null,4,5]"

, just the same as
how LeetCode OJ serializes a binary tree. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.
Note: Do not use class member/global/static variables to store states. Your serialize and deserialize algorithms should be stateless.

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Codec:

def _serialize(self, root):
if root == None:
self.myList.append('x')
else:
self.myList.append(str(root.val))
self._serialize(root.left)
self._serialize(root.right)

def _deserialize(self, dList):

if dList[self.idx] == 'x':
return None

node = TreeNode(dList[self.idx])

self.idx = self.idx+1
node.left = self._deserialize(dList)

self.idx = self.idx+1
node.right = self._deserialize(dList)

return node

def serialize(self, root):
"""Encodes a tree to a single string.

:type root: TreeNode
:rtype: str
"""
self.myList = []
self._serialize(root)
return " ".join(self.myList);

return self.retString

def deserialize(self, data):
"""Decodes your encoded data to tree.

:type data: str
:rtype: TreeNode
"""
self.idx = 0;
dList = data.split(" ")
return self._deserialize(dList)

# Your Codec object will be instantiated and called as such:
# codec = Codec()
# codec.deserialize(codec.serialize(root))