景岁的Leetcode解题报告：297. Serialize and Deserialize Binary Tree(Python)

一种基于前序遍历的解法。

# Definition for a binary tree node.# class TreeNode(object):#     def __init__(self, x):#         self.val = x#         self.left = None#         self.right = Noneimport Queue# 本解法是基于层次遍历的。序列化和反序列化中的队列中都会有None，但是循环时读到None时不会读它的左右节点。另外可以参考水中的鱼的前序遍历解法：# http://fisherlei.blogspot.jp/2013/03/interview-serialize-and-de-serialize.htmlclass Codec:    def serialize(self, root):        """Encodes a tree to a single string.        :type root: TreeNode        :rtype: str        """        if root is None:            return ''        list = []        list.append(root)        i = 0        # 优化的层次遍历，不使用Queue，直接使用一个list存储和遍历。        while i < len(list):            if list[i] is not None:                list.append(list[i].left)                list.append(list[i].right)            i += 1        # 将list打印成逗号分隔的字符串        res_str = ''        for j in range(len(list)):            if list[j] is not None:                res_str += str(list[j].val) + ','            else:                res_str += 'x' + ','        return res_str[0:-1]    def deserialize(self, data):        """Decodes your encoded data to tree.        :type data: str        :rtype: TreeNode        """        if data == '':            return None        input = data.split(',')        root = TreeNode(input[0])        q = Queue.Queue(-1)        q.put(root)        i = 0        # 逻辑是使用队列循环节点，然后有一个计数器，如果节点不是'x'，则计数器加2        while q.qsize() > 0 and i + 2 < len(input):            node = q.get()            if node.val != 'x':                i += 1                left = TreeNode(input[i])                if left.val != 'x':                    node.left = left                    q.put(left)                i += 1                right = TreeNode(input[i])                if right.val != 'x':                    right = TreeNode(input[i])                    node.right = right                q.put(right)        return root# Your Codec object will be instantiated and called as such:# codec = Codec()# codec.deserialize(codec.serialize(root))