head of a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.
For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.
Input: head = [-10,-3,0,5,9]
Explanation: One possible answer is [0,-3,9,-10,null,5], which represents the shown height balanced BST.
Input: head = 
- The number of nodes in
headis in the range
[0, 2 * 104].
-105 <= Node.val <= 105