剑指 Offer 37. 序列化二叉树

题目：https://leetcode-cn.com/problems/xu-lie-hua-er-cha-shu-lcof/
转载自：https://leetcode-cn.com/problems/xu-lie-hua-er-cha-shu-lcof/solution/mian-shi-ti-37-xu-lie-hua-er-cha-shu-ceng-xu-bian-/

# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Codec:
    def serialize(self, root):
        if not root: return "[]"
        queue = collections.deque()
        queue.append(root)
        res = []
        while queue:
            node = queue.popleft()
            if node:
                res.append(str(node.val))
                queue.append(node.left)
                queue.append(node.right)
            else: res.append("null")
        return '[' + ','.join(res) + ']'

    def deserialize(self, data):
        if data == "[]": return
        vals, i = data[1:-1].split(','), 1
        root = TreeNode(int(vals[0]))
        queue = collections.deque()
        queue.append(root)
        while queue:
            node = queue.popleft()
            if vals[i] != "null":
                node.left = TreeNode(int(vals[i]))
                queue.append(node.left)
            i += 1
            if vals[i] != "null":
                node.right = TreeNode(int(vals[i]))
                queue.append(node.right)
            i += 1
        return root
        

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