Closest Binary Search Tree Value Variant (LeetCode 270)

Given a BST and a target value, return the tree value closest to the target. Examples Example 1: Input: root = [4,2,5,1,3], target = 3.714286 Output: 4 Explanation: |4 - 3.714| = 0.286 is smaller than |3 - 3.714| = 0.714. Example 2: Input: root = [1], target = 4.428571 Output: 1 Example 3: Input: root = [2,1,3], target = 2.5 Output: 2 Explanation: Both 2 and 3 are 0.5 away from 2.5; return the smaller value. Constraints 1 <= number of nodes <= 10^4 0 <= Node.val <= 10^9 -10^9 <= target <= 10^9