145.二叉树的后序遍历.py

#
# @lc app=leetcode.cn id=145 lang=python3
#
# [145] 二叉树的后序遍历
#


# @lc code=start
# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def postorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
        res = []
        if root:
            if root.left:
                res.extend(self.postorderTraversal(root.left))
            if root.right:
                res.extend(self.postorderTraversal(root.right))
            res.append(root.val)
        return res


# @lc code=end