题解 | 二叉树的后序遍历-递归写法

# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param root TreeNode类 
# @return int整型一维数组
#
class Solution:
    def postorderTraversal(self , root: TreeNode) -> List[int]:
        # write code here
        # 递归
        res=[]
        if root is None:
            return res 
        def  dfs(root):
            if root.left:
                dfs(root.left)
            if root.right:
                dfs(root.right)
            res.append(root.val)
        dfs(root)
        return res