Leetcode 270. Closest Binary Search Tree Value

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.

Analysis:

Maintain a min value and update it with left and right .

Time complexity: O(logn)

Space complexity: O(1)

Code is below:

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public int closestValue(TreeNode root, double target) {
        // O(logn)
        
        int min = root.val;
        
        while (root != null) {
            min = Math.abs(target - root.val) < Math.abs(target - min) ? root.val : min;
            root = root.val < target ? root.right : root.left;
        }
        
        return min;
    }
}