题解 | #二叉树的后序遍历#

class Solution:
    def postorderTraversal(self , root: TreeNode) -> List[int]:
        ans=[]
        def postorder(root):
            if not root: return 
            if root.left:
                postorder(root.left)
            if root.right:
                postorder(root.right)
            ans.append(root.val)
        postorder(root)
        return ans