Java 算法：查找数组中与目标值最接近的三个数

以下是 Java 代码实现：

import java.util.*;

public class ClosestThreeNumbers {
    public static Map<String, Integer> findClosest(int[] nums, int target) {
        Map<String, Integer> result = new HashMap<>();
        if (nums == null || nums.length < 3) {
            return result;
        }
        Arrays.sort(nums);
        int diff = Integer.MAX_VALUE;
        for (int i = 0; i < nums.length - 2; i++) {
            int left = i + 1, right = nums.length - 1;
            while (left < right) {
                int sum = nums[i] + nums[left] + nums[right];
                if (Math.abs(sum - target) < diff) {
                    diff = Math.abs(sum - target);
                    result.put('number1', nums[i]);
                    result.put('number2', nums[left]);
                    result.put('number3', nums[right]);
                }
                if (sum < target) {
                    left++;
                } else if (sum > target) {
                    right--;
                } else {
                    return result;
                }
            }
        }
        return result;
    }

    public static void main(String[] args) {
        int[] nums = {1, 3, 5, 7, 9, 12, 15};
        int target = 20;
        Map<String, Integer> result = findClosest(nums, target);
        System.out.println(result.toString()); // Output: {number1=7, number2=9, number3=12}
    }
}

该算法的时间复杂度为$O(n^2)$，因为需要两层循环遍历数组。如果数组长度很大，性能可能会受到影响。