得物笔试ac

第一题以最后一个元素为中心一直往前环就可以

注意边界条件可能是a[1]-a[0]。

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        for (int i = 0; i < a.length; i++) {
            a[i] = sc.nextInt();
        }
        Arrays.sort(a);
        int max = a[1] - a[0];
        if (n > 2) {
            max = a[2] - a[0];
        }
        int i = n - 2;
        while (i >= 2) {
            int cur = Math.max(a[i + 1] - a[i - 1], a[i] - a[i - 2]);
            max = Math.max(max, cur);
            i -= 2;
        }
        System.out.print(max);
    }
}

第二题，记录所有数字求和到n的最小次数

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int N = scanner.nextInt();
        int M = scanner.nextInt();
        int[] numbers = new int[N];
        for (int i = 0; i < N; i++) {
            numbers[i] = scanner.nextInt();
        }
        Arrays.sort(numbers);
        int result = findMinNumbers(numbers, M);
        if (result == Integer.MAX_VALUE) {
            System.out.println("No solution");
        } else {
            System.out.println(result);
        }
    }
    public static int findMinNumbers(int[] numbers, int target) {
        int[] dp = new int[target + 1];
        Arrays.fill(dp, Integer.MAX_VALUE);
        dp[0] = 0;
        for (int num : numbers) {
            for (int i = target; i >= num; i--) {
                if (dp[i - num] != Integer.MAX_VALUE) {
                    dp[i] = Math.min(dp[i], dp[i - num] + 1);
                }
            }
        }
        return dp[target];
    }
}