最接近的二叉搜索树值

/* 
 * Problem: Closest Binary Search Tree Value
 * Approach using Java Streams:
 * 1. Convert the BST to a list using an in-order traversal.
 * 2. Use Java Streams to find the closest value to the target.
 */
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
 
public class Solution {
    public int closestValue(TreeNode root, double target) {
        // In-order traversal to convert BST to a sorted list
        List<Integer> values = new ArrayList<>();
        inOrderTraversal(root, values);
        // Find the closest value using Streams
        return values.stream()
                .min((a, b) -> Double.compare(Math.abs(a - target), Math.abs(b - target)))
                .orElseThrow(() -> new IllegalArgumentException("Tree is empty"));
    }
 
    private void inOrderTraversal(TreeNode node, List<Integer> values) {
        if (node != null) {
            inOrderTraversal(node.left, values);
            values.add(node.val);
            inOrderTraversal(node.right, values);
        }
    }
}