Closest Binary Search Tree Value

Given the root of a binary search tree and a target value, return the value in the BST that is closest to the target. If there are multiple answers, return the smallest such value.

A binary search tree satisfies these constraints:

• The left subtree of every node contains only nodes with keys less than the node's key.
• The right subtree of every node contains only nodes with keys greater than the node's key.
• Both the left and right subtrees are also BSTs.

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