# Definition for a binary tree node.# class TreeNode:#     def __init__(self, x):#         self.val = x#         self.left = None#         self.right = Noneclass Solution:    def zigzagLevelOrder(self, root: TreeNode) -> List[List[int]]:        from collections import deque        if not root:            return []        queue=deque()        queue.append(root)        res=[]        level=0        while queue:            tmp=deque()            for i in range(len(queue)):                t=queue.popleft()                if level%2==0:                    tmp.append(t.val)                                else:                    tmp.appendleft(t.val)                if t.left:                    queue.append(t.left)                if t.right:                    queue.append(t.right)            level+=1            res.append(list(tmp))        return res