Given the root node of a binary search tree, return the sum of values of all nodes with value between L and R (inclusive).
The binary search tree is guaranteed to have unique values.
Input: root = [10,5,15,3,7,null,18], L = 7, R = 15
Input: root = [10,5,15,3,7,13,18,1,null,6], L = 6, R = 10
- The number of nodes in the tree is at most 10000.
- The final answer is guaranteed to be less than 2^31.