270. Closest Binary Search Tree Value
Binary search: Go left if target is smaller than current root value, and go right otherwise. Choose the closest to target value at each step.
Time = O(h), space = O(1)
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public int closestValue(TreeNode root, double target) {
int closest = root.val;
while (root != null) {
int val = root.val;
closest = Math.abs(val - target) < Math.abs(closest - target) ? val : closest;
root = target < root.val ? root.left : root.right;
}
return closest;
}
}