Find closest value to a target in a BST
Company: DoorDash
Role: Machine Learning Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Onsite
## 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`
Quick Answer: This question evaluates understanding of binary search tree properties and numeric approximation, measuring competence in tree traversal, comparison logic, and algorithmic efficiency under input-size constraints.