题解 | #最大子矩阵#

如果能装换为一维数组求最大的连续子序列就好了。

把二维数组压扁，dp数组每一行代表以上列的和，然后枚举n行到0行（n行减上面的行就是这两行之间的行）之间可能的最大连续子序列即可。

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    static int res = Integer.MIN_VALUE;
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[][] arr = new int[n][n];
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                arr[i][j] = in.nextInt();
            }
        }
        if (n==1){
            System.out.println(arr[0][0]);
            return;
        }
        int[][] dp = new int[n][n];
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                if (i == 0) {
                    dp[i][j] = arr[i][j];
                } else {
                    dp[i][j] = arr[i][j] + dp[i - 1][j];
                }
            }
        }
        int[] x = new int[n];
        for (int i = 0; i < n; i++) {
            for (int j = 0; j <= i; j++) {
                if (i == j) {
                    x = dp[i];
                    dfs(x);
                } else if (j < i) {
                    x = fun(dp[i], dp[j]);
                    dfs(x);
                } 

            }

        }
        System.out.println(res);

    }

    private static void dfs(int[] x) {
        int[] dp = new int[x.length];
        dp[0] = x[0];
        res = Math.max(dp[0], res);
        for (int i = 1; i < dp.length; i++) {
            dp[i] = Math.max(dp[i - 1] + x[i], x[i]);
            res = Math.max(dp[i], res);
        }

    }

    private static int[] fun(int[] ints, int[] ints1) {
        int[] ints2 = new int[ints.length];
        for (int i = 0; i < ints2.length; i++) {
            ints2[i] = ints[i] - ints1[i];
        }
        return ints2;
    }
}