题解 | #Tree# #将二叉搜索树改为累加树#

#coding:utf-8
# 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 TreeNode类
#
class Solution:
    def __init__(self):
        self.summation = 0

    def convertBST(self , root ):
        # write code here
        #思路：既然找最大的，那就是遍历所有右子树
        if root == None:
            return root 
        self.dfs(root)
        return root
    
    def dfs(self, root):
        if root == None:
            return 
        self.dfs(root.right)
        self.summation += root.val
        root.val = self.summation
        self.dfs(root.left)
        return