层序遍历,然后按照输出结果逆序

# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param root TreeNode类 
# @return int整型二维数组
#
class Solution:
    def levelOrderBottom(self , root: TreeNode) -> List[List[int]]:
        # write code here
        if not root:
            return []
        q = [root]
        res = []
        while q:
            n, v = [], []
            for node in q:
                v.append(node.val)
                if node.left:
                    n.append(node.left)
                if node.right:
                    n.append(node.right)
            res.append(v)
            q = n
        return res[::-1]