leetcode 297. 二叉树的序列化与反序列化

发表于 分类于 阅读次数：

思路

前序遍历 序列化 二叉树 为 字符串
前序遍历 反序列化 字符串 为 二叉树
注意叶子节点的处理

时间复杂度

O(n) n为节点数

空间复杂度

O(n) n为节点数

代码

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# 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
        """
        if not root:
            return 'None'
        return f'{root.val},{self.serialize(root.left)},{self.serialize(root.right)}'
        

    def deserialize(self, data):
        """Decodes your encoded data to tree.
        
        :type data: str
        :rtype: TreeNode
        """
        def build_tree(node_list):
            if not node_list:
                return

            node = node_list.pop(0)
            if node == 'None':
                return
                
            root = TreeNode(node)
            root.left = build_tree(node_list)
            root.right = build_tree(node_list)
            return root

        return build_tree(data.split(','))
        

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