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]. Example 1: Input: root = [10,5,15,3,7,null,18], low = 7, high = 15 Output: 32 Example 2: Input: root = [10,5,15,3,7,13,18,1,null,6], low = 6, high = 10 Output: 23 Constraints: The number of nodes in the tree is in the range [1, 2 * 104]. 1 <= Node.val <= 105 1 <= low <= high <= 105 All Node.val are unique.