Given a binary search tree with non-negative values, find the minimum absolute difference between values of any two nodes.
Example:
Input:
1
\
3
/
2
Output:
1
Explanation:
The minimum absolute difference is 1, which is the difference between 2 and 1 (or between 2 and 3).
Note:
- There are at least two nodes in this BST.
- This question is the same as 783: https://leetcode.com/problems/minimum-distance-between-bst-nodes/