[270. Closest Binary Search Tree Value] #leetcode

270_0903.java

// O(log(n)) O(1) 
class Solution {
    public int closestValue(TreeNode root, double target) {
        int a = root.val;
        TreeNode kid = target < a ? root.left : root.right;
        
        if (kid == null) return a;
        int b = closestValue(kid, target);
        
        return Math.abs(a - target) < Math.abs(b - target) ? a : b;
    }
}

class Solution1 {
    public int closestValue(TreeNode root, double target) {
        int closest = root.val;
        while (root != null) {
            if (Math.abs(closest - target) >= Math.abs(root.val - target)) {
                closest = root.val;
            }
            root = target < root.val ? root.left : root.right;
        }
        
        return closest;
    }
}