LeetCode 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