思路

1. 高维 dp，开四维（i，j，k，l）表示两个人的位置，进行暴力状态转移。

代码

#include <bits/stdc++.h>
using namespace std;
#define db  double
#define ll  long long
#define Pir pair<int, int>
#define fi  first
#define se  second
#define pb  push_back
#define m_p make_pair
#define inf 0x3f3f3f3f
#define INF 0x3f3f3f3f3f3f3f3f
/*==========ACMer===========*/
#define Max(a, b, c, d) max(max(a, b), max(c, d))
const int N = 55;
int a[N][N];
int dp[N][N][N][N];


int main()
{
    
    
    memset(dp, 0, sizeof dp);
    int n, m; 
    scanf("%d %d", &n, &m);
    for (int i = 1; i <= n; i ++)
        for (int j = 1; j <= m; j ++)
            scanf("%d" ,&a[i][j]);

    for (int i = 1; i <= n; i ++) {
    
    
        for (int j = 1; j <= m; j ++) {
    
    
            for (int k = 1; k <= n; k ++) {
    
    
                for (int l = 1; l <= m; l ++) {
    
    
                    int res = (i == k && j == l) ? (a[i][j]) : (a[i][j] + a[k][l]);
                    dp[i][j][k][l] = Max(dp[i - 1][j][k - 1][l], dp[i - 1][j][k][l - 1], dp[i][j - 1][k - 1][l], dp[i][j - 1][k][l - 1]) + res;
                }
            }
        }
    }

    printf("%d\n", dp[n][m][n][m]);

    return 0;
}