LeetCode 270. Closest Binary Search Tree Value

原题链接在这里：https://leetcode.com/problems/closest-binary-search-tree-value/

题目：

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

题解：

target 一定在找的path 上，若是出现了比minDiff 还小的 差值，就把改点更新为cloest.

但注意target 是 double, 会有溢出情况，所以minDiff 初始化成Double.MAX_VALUE.

Time Complexity: O(h). h 是树的高度. Space: O(1).

AC Java:

/**
 * 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) {
        if(root == null){
            return -1;
        }
        
        int cloest = root.val;
        double minDiff = Double.MAX_VALUE;
        
        while(root != null){
            if(Math.abs(root.val - target) < minDiff){
                minDiff = Math.abs(root.val - target);
                cloest = root.val;
            }
            if(target > root.val){
                root = root.right;
            }else if(target < root.val){
                root = root.left;
            }else{
                return root.val;
            }
        }
        return cloest;
    }
}

 跟上Closest Binary Search Tree Value II