题解 | #二叉树的后序遍历#

# 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
#
# 与前序和中序相同，只不过交换一下顺序
class Solution:
    def postorderTraversal(self , root: TreeNode) -> List[int]:
        if not root:
            return None

        def bhdSequence(r):
            l = []
            if r.left:
                l.extend(bhdSequence(r.left))
            if r.right:
                l.extend(bhdSequence(r.right))
            l.append(r.val)
            return l

        return bhdSequence(root)