Range Sum of BST. Any language, any approach

Given a binary search tree bst and two integers low and high, return the sum of values of all nodes with a value in the inclusive range [low, high]. (All node values are unique.) -- Example 1 -- Input: bst =[10,5,15,3,7,null,18], low =7, high =15 (see Figure 1) Output: 32 Explanation: Nodes 7,10 , and 15 are in the range [7,15].7+10+15=32. -- Example 2 -- Input: bst =[10,5,15,3,7,13,18,1,null,6], low =6, high =10 (see Figure 2) Output: 23 Explanation: Nodes 6,7 , and 10 are in the range [6,10].6+7+10=23. Figure 1 rigure