297.serialize-and-deserialize-binary-tree.py

#
# @lc app=leetcode id=297 lang=python3
#
# [297] Serialize and Deserialize Binary Tree
#

# @lc code=start
# 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):
        """Encodes a tree to a single string.

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

        rtn = []

        def dfs(node):
            # nonlocal rtn
            if node is None:
                rtn.append("X")
            else:
                rtn.append(str(node.val))
                dfs(node.left)
                dfs(node.right)
        dfs(root)
        return " ".join(rtn)

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

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

        vals = iter(data.split())

        def dfs():
            val = next(vals)
            if val == "X":
                return None
            node = TreeNode(int(val))
            node.left = dfs()
            node.right = dfs()
            return node

        return dfs()


# Your Codec object will be instantiated and called as such:
# ser = Codec()
# deser = Codec()
# ans = deser.deserialize(ser.serialize(root))
# @lc code=end