590. N-ary Tree Postorder Traversal

"""
# Definition for a Node.
class Node(object):
    def __init__(self, val, children):
        self.val = val
        self.children = children
"""
class Solution(object):
    def postorder(self, root):
        
 
"""
        :type root: Node
        :rtype: List[int]
        """
        res=[]
        if root==None:
            return res
        stack=[root]
        while stack:
            curr=stack.pop()
            res.append(curr.val)
            stack.extend(curr.children)
        return res[::-1]
        
        
 

反思：1.列表的常見操作不熟悉

　　2.怎麼用list來處理樹結構，不知道

strategy：

   1.用anki記憶一些list的常見操作

  2.知道迭代和遞迴的區別