Find closest value to a target in a BST

Q: Find closest value to a target in a BST

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Question

Problem

Given the root of a binary search tree (BST) and a floating-point number target, return the value in the BST that is closest to target.

If there are multiple values equally close, return the smaller value (or specify a deterministic tie-breaker).

Input

root : root node of a BST (each node has val , left , right )
target : a real number

Output

An integer value from the BST

Constraints

Number of nodes: 1 .. 10^5
Node values are integers in a reasonable range (e.g., 32-bit signed)
Tree may be unbalanced

Example

BST values: [4,2,5,1,3], target = 3.714286 → output 4