朴素班三维dp

static int[][][] f = new int[N][4][M];
理论上192MB会MLE

import java.util.*;

public class Main {
    static final int N = 100010, M = 1010;
    static int[][][] f = new int[N][4][M];
    static int[] a = new int[N];

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt(), m = sc.nextInt();
        sc.nextLine();

        String[] s = sc.nextLine().split(" ");
        for (int i = 1; i <= n; i++) a[i] = Integer.parseInt(s[i - 1]);

        for (int i = 0; i < n; i++)
            for (int j = 0; j < m; j++) {
                if (j != 0) f[i][0][j] = -0x3f3f3f3f;
                else f[i][0][j] = 0;
            }

        for (int i = 1; i <= n; i++)
            for (int j = 1; j <= 3; j++)
                for (int k = 0; k < m; k++) 
                    f[i][j][k] = Math.max(f[i - 1][j][k], f[i - 1][j - 1][((k - a[i]) % m + m) % m] + a[i]);

        int ans = -1;
        for (int i = 1; i <= n; i++) 
            if (ans < f[i][3][0]) ans = f[i][3][0];

        System.out.println(ans);
    }
}

10/12

import java.util.*;

public class Main {
    static final int N = 1010;
    static int[][][] f = new int[3 * N][4][N];
    static ArrayList<Integer>[] list = new ArrayList[N];

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt(), m = sc.nextInt();
        sc.nextLine();
        for (int i = 0; i < N; i++) list[i] = new ArrayList<>();

        String[] s = sc.nextLine().split(" ");
        for (int i = 1; i <= n; i++) {
            int x = Integer.parseInt(s[i - 1]);
            list[x % m].add(x);
        }

        for (int i = 0; i < 3 * N; i++)
                Arrays.fill(f[i][0], -0x3f3f3f3f);

        for (int i = 0; i <= 3 * m; i++) f[i][0][0] = 0;

        int cnt = 0;
        for (int i = 0; i < m; i++) {
            list[i].sort(Comparator.reverseOrder());
            for (int u = 0; u < Math.min(3, list[i].size()); u++) {
                int x = list[i].get(u);
                cnt++;
                for (int j = 1; j <= 3; j++)
                    for (int k = 0; k < m; k++)
                        f[cnt][j][k] = Math.max(f[cnt - 1][j][k], f[cnt - 1][j - 1][((k - x) % m + m) % m] + x);
            }
        }

        int ans = -1;
        for (int i = 1; i <= 3 * m; i++)
            if (ans < f[i][3][0]) ans = f[i][3][0];

        System.out.println(ans);
    }
}