text: #LeetCode problem 938: Range Sum of BST
  # Definition for a binary tree node.
  # class TreeNode:
  #     def __init__(self, val=0, left=None, right=None):
  #         self.val = val
  #         self.left = left
  #         self.right = right
  class Solution:
      def rangeSumBST(self, root: TreeNode, L: int, R: int) -> int:
          s=[]
          self.returnSum(root, L, R, s)
          return(sum(s))
      
      def returnSum(self, root: TreeNode, L: int, R: int, s:List):   
          if root is None:
              return 
          if root.val<=R and root.val>=L:
              s.append(root.val)
          self.returnSum(root.left, L, R, s)
          self.returnSum(root.right, L, R, s)