590. N叉树的后序遍历

一、590. N叉树的后序遍历 1.1、题目描述

1.2.1、递归

"""
# Definition for a Node.
class Node:
    def __init__(self, val, children):
        self.val = val
        self.children = children
"""
class Solution:
    def __init__(self) ->None:
        self.ret = []
    def postorder(self, root: 'Node') -> List[int]:
        if not root:
            return []
        self.postorderT(root)
        return self.ret
        
    def postorderT(self, root: 'Node') -> List[int]:
        if root.children:
            for child in root.children:
                self.postorder(child)
        if root:
            self.ret.append(root.val)

1.2.2、迭代

class Solution:
    def __init__(self) ->None:
        self.ret = []
    def postorder(self, root: 'Node') -> List[int]:
        if not root:
            return []
        
        que = [root]
        
        while que:
            node = que.pop()
            if node:
                self.ret.append(node.val)
            
            for child in node.children:
                que.append(child)
        # 逆序
        return self.ret[::-1]