145.binary-tree-postorder-traversal.py

#
# @lc app=leetcode id=145 lang=python3
#
# [145] Binary Tree Postorder Traversal
#

# @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 = []

        def dfs(root):
            if root is None:
                return
            dfs(root.left)
            dfs(root.right)
            res.append(root.val)
        dfs(root)
        return res

# @lc code=end