# 938. Range Sum of BST

https://leetcode.com/problems/range-sum-of-bst/

# 思路：
1. 就是基本的BFS 加上一些運算技巧

# 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: Optional[TreeNode], low: int, high: int) -> int:
        
        from collections import deque 
        list=[]
        q=deque()
        q.append(root)
        
        while q :
            root=q.popleft()
            list.append(root.val)
        
            if root.left: 
                q.append(root.left)
            if root.right :
                q.append(root.right )
            
      
       
        list.sort()
        flag=0
        sum=0
        for i in list :
            
            if i ==low:
                flag=1 
            if i ==high :
                sum+=high 
                return sum 
            if flag==1:
                sum+=i