270. Closest Binary Search Tree Value

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270. Closest Binary Search Tree Value

Description

Given the root of a binary search tree and a target value, return the value in the BST that is closest to the target. If there are multiple answers, print the smallest.

Example 1:

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Input: root = [4,2,5,1,3], target = 3.714286
Output: 4

Example 2:

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Input: root = [1], target = 4.428571
Output: 1

Constraints:

  • The number of nodes in the tree is in the range [1, 10^4].
  • 0 <= Node.val <= 10^9
  • -10^9 <= target <= 10^9

Hints/Notes

  • 2024/02/15
  • bst
  • premium

Solution

Language: C++

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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int res = INT_MAX;

    int closestValue(TreeNode* root, double target) {
        traverse(root, target);
        return res;
    }

    void traverse(TreeNode* root, double target) {
        if (!root) {
            return;
        }
        if (root->val == target) {
            res = root->val;
        } else if (root->val > target) {
            if (abs(root->val - target) < abs(res - target)) {
                res = root->val;
            }
            traverse(root->left, target);
        } else {
            if (abs(root->val - target) <= abs(res - target)) {
                res = root->val;
            }
            traverse(root->right, target);
        }
    }
};