270. Closest Binary Search Tree Value 二叉搜索树中，距离目标值最近的节点
作者：互联网
Given the root of a binary search tree and a target value, return the value in the BST that is closest to the target.
Example 1:
Input: root = [4,2,5,1,3], target = 3.714286 Output: 4
Example 2:
Input: root = [1], target = 4.428571 Output: 1
标签：Binary,Search,target,Closest,value,Output,Input,root,Example 来源： https://www.cnblogs.com/immiao0319/p/14975118.html