LintCode 900. Closest Binary Search Tree Value

最新推荐文章于 2021-01-08 07:11:09 发布

原创最新推荐文章于 2021-01-08 07:11:09 发布 · 217 阅读

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本文介绍了一种有效的方法，通过中序遍历二叉搜索树来找到最接近给定目标值的节点值。这种方法适用于目标值为浮点数的情况，并保证了在树中存在唯一最接近的目标值。

Closest Binary Search Tree Value
中文English
Given a non-empty binary search tree and a target value, find the value in the BST that is closest to the target.

Example
Example1

Input: root = {5,4,9,2,#,8,10} and target = 6.124780
Output: 5
Example2

Input: root = {3,2,4,1} and target = 4.142857
Output: 4
Notice
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.

解法1：
InOrder Traversal。
注意: target是double，要注意转换！
代码如下:

/**
 * Definition of TreeNode:
 * class TreeNode {
 * public:
 *     int val;
 *     TreeNode *left, *right;
 *     TreeNode(int val) {
 *         this->val = val;
 *         this->left = this->right = NULL;
 *     }
 * }
 */

class Solution {
public:
    /**
     * @param root: the given BST
     * @param target: the given target
     * @return: the value in the BST that is closest to the target
     */
    int closestValue(TreeNode * root, double target) {
        if (!root) return 0;
        minGap = (double)INT_MAX;
        result = root->val;
        inOrderTraversal(root, target);
        return result;
    }

private:
    void inOrderTraversal(TreeNode * root, double target) {
        if (!root) return;
        inOrderTraversal(root->left, target);
        double gap = abs((double)root->val - target);
        if (gap < minGap) {
            minGap = gap;
            result = root->val;
        }
        inOrderTraversal(root->right, target)
;    }
    
    int result;
    double minGap;
};