LeetCode Closest Binary Search Tree Value

Posted 2020-06-14

原题链接在这里：https://leetcode.com/problems/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.

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:

 1 /**
 2  * Definition for a binary tree node.
 3  * public class TreeNode {
 4  *     int val;
 5  *     TreeNode left;
 6  *     TreeNode right;
 7  *     TreeNode(int x) { val = x; }
 8  * }
 9  */
10 public class Solution {
11     public int closestValue(TreeNode root, double target) {
12         if(root == null){
13             return -1;
14         }
15         
16         int cloest = root.val;
17         double minDiff = Double.MAX_VALUE;
18         
19         while(root != null){
20             if(Math.abs(root.val - target) < minDiff){
21                 minDiff = Math.abs(root.val - target);
22                 cloest = root.val;
23             }
24             if(target > root.val){
25                 root = root.right;
26             }else if(target < root.val){
27                 root = root.left;
28             }else{
29                 return root.val;
30             }
31         }
32         return cloest;
33     }
34 }

 跟上Closest Binary Search Tree Value II