Closest Binary Search Tree Value

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已于 2022-04-23 06:45:31 修改

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分类专栏： Tree traverse 文章标签： leetcode

于 2016-07-12 04:21:22 首次发布

本文链接：https://blog.youkuaiyun.com/u013325815/article/details/51885474

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本文介绍了一种在二叉搜索树中寻找最接近目标值的方法。通过遍历树并记录与目标值差值最小的节点，可以在O(log n)的时间复杂度内找到最接近的目标值。

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.

思路：就是traverse，记录一个diff，然后logn去搜，搜到底，就可以了；

/**
 * 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 res = root.val;
        double diff = Double.MAX_VALUE;
        while(root != null) {
            if(root.val == target) {
                return root.val;    
            } else if(root.val < target) {
                if(target - root.val < diff) {
                    diff = target - root.val;   
                    res = root.val;
                }
                root = root.right;
            } else {
                // root.val > target;
                if(root.val - target < diff) {
                    diff = root.val - target;   
                    res = root.val;
                }
                root = root.left;
            }
        }
        return res;
    }
}