[LeetCode] Closest Binary Search Tree Value

Problem

Given a non-empty binary search tree and a target value, find the value in the BST that is closest to the target.

Note

Given target value is a floating point.
You are guaranteed to have only one unique value in the BST that is closest to the target.

Example

Input: root = [4,2,5,1,3], target = 3.714286

    4
   / \
  2   5
 / \
1   3

Output: 4

Solution

class Solution {
    public int closestValue(TreeNode root, double target) {
        if (root == null) return 0;
        TreeNode child = root.val < target ? root.right : root.left;
        if (child == null) return root.val;
        int closest = closestValue(child, target);
        return Math.abs(root.val-target) < Math.abs(closest-target) ? root.val : closest;
    }
}