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.
Example 1:
Input: root = [10,5,15,3,7,null,18], L = 7, R = 15 Output: 32
Example 2:
Input: root = [10,5,15,3,7,13,18,1,null,6], L = 6, R = 10 Output: 23
Note:
<li>The number of nodes in the tree is at most <code>10000</code>.</li>
<li>The final answer is guaranteed to be less than <code>2^31</code>.</li>