297.py

'''
 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.

 Example: 

 You may serialize the following tree:

 1
 / \
 2 3
 / \
 4 5

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

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

classCodec:

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

 :type root: TreeNode
 :rtype: str
 """

defpreorder(root):
ifroot:
seralizeTree.append(str(root.val) +',')
preorder(root.left)
preorder(root.right)
else:
seralizeTree.append('#,')

seralizeTree= []
preorder(root)
return''.join(seralizeTree)


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

 :type data: str
 :rtype: TreeNode
 """

defbuildTree(preorder):
value=preorder.pop(0)
ifvalue=='#':
returnNone

node=TreeNode(int(value))
node.left=buildTree(preorder)
node.right=buildTree(preorder)
returnnode

preorder=data.split(',')[:-1]
returnbuildTree(preorder)


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