LeetCode 297 - 二叉树的序列化与反序列化

class Codec:

    def serialize(self, root):
        """Encodes a tree to a single string.
        
        :type root: TreeNode
        :rtype: str
        """
        retStr = []
        def serializeIMPL(root):
            nonlocal retStr
            if not root:
                return
            retStr.append(root.val)
            if root.left:
                serializeIMPL(root.left)
            else:
                # 如果是空则直接返回非法值，无需关注树是否是满二叉树
                retStr.append(sys.maxsize)
            if root.right:
                serializeIMPL(root.right)
            else:
                retStr.append(sys.maxsize)
        serializeIMPL(root)
        # 用逗号把列表转变为字符串返回
        return ",".join(map(str, retStr))
        

    def deserialize(self, data):
        """Decodes your encoded data to tree.
        
        :type data: str
        :rtype: TreeNode
        """
        # 处理字符串为空的情况
        if not data:
                return None
        # 把字符串重新解析为列表
        values = deque(map(int, data.split(",")))
        def deserializeIMPL():
            if not values:
                return None
            val = values.popleft()
            if val == sys.maxsize:
                return None
            node = TreeNode(val)

            先根遍历产生树
            node.left = deserializeIMPL()
            node.right = deserializeIMPL()
            return node

        return deserializeIMPL()

        

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