题目
Given the root node of a binary search tree, return the sum of values of all nodes with a value in the range [low, high].
解题思路
递归，如果当前节点在范围内，加到结果里。如果当前节点大于low，遍历左子树，小于high，遍历右子树
代码
class Solution:
class Solution:
def rangeSumBST(self, root: TreeNode, low: int, high: int) -> int:
def dfs(root):
if root:
if low <= root.val <= high:
self.res += root.val
if low < root.val:
dfs(root.left)
if high > root.val:
dfs(root.right)
self.res = 0
dfs(root)
return self.res
