1 class Solution: 2     def __init__(self): 3         self.L = list() 4  5     def inOrder(self,node): 6         if node!=None: 7             if node.left != None: 8                 self.inOrder(node.left) 9 10             self.L.append(node)11 12             if node.right != None:13                 self.inOrder(node.right)14 15     def bstToGst(self, root: TreeNode) -> TreeNode:16         self.inOrder(root)17         sums = 018         for i in range(len(self.L)-1,-1,-1):19             sums += self.L[i].val20             self.L[i].val = sums21 22         return root