【Leetcode_总结】145. 二叉树的后序遍历 - python

Q:

给定一个二叉树，返回它的 后序 遍历。

示例:

输入: [1,null,2,3]  
   1
    \
     2
    /
   3 

输出: [3,2,1]

进阶: 递归算法很简单，你可以通过迭代算法完成吗？

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链接：https://leetcode-cn.com/problems/binary-tree-postorder-traversal/description/

思路：递归 后续遍历

代码：

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def postorderTraversal(self, root):
        """
        :type root: TreeNode
        :rtype: List[int]
        """
        if root == None:
            return []
        else:
            res = []
            self.later_digui(root, res)
        return res
    
    def later_digui(self,root,res):
        if root == None:
            return
        self.later_digui(root.left,res)
        self.later_digui(root.right,res)
        res.append(root.val)