'''
Description: 
Autor: Au3C2
Date: 2021-03-25 16:14:42
LastEditors: Au3C2
LastEditTime: 2021-03-25 16:26:17
'''
class Solution:
    def convertBST(self, root: TreeNode) -> TreeNode:
        self.sumVal = 0
        self.dfs(root)
        return root
    def dfs(self,root):
        if not root:
            return 0
        self.dfs(root.right)
        self.sumVal += root.val
        root.val = self.sumVal
        self.dfs(root.left)

# 树，中等。奇怪的题目，同 【1038. 把二叉搜索树转换为累加树】，就不另外写了
# https://leetcode-cn.com/problems/convert-bst-to-greater-tree/