C++ :

#include<iostream>
#define N 51
using namespace std;
int max(int a,int b){return a>b?a:b;}
int sum[N][N][N][N]={0};
int c[N][N]={0};
int main()
{
    int n,m,i,j,h,k,a,b;
    cin>>m>>n;
    for(i=1;i<=m;i++)
      for(j=1;j<=n;j++)
        cin>>c[i][j];
    for(i=1;i<=m;i++)
      for(j=1;j<=n;j++)
        for(h=1;h<=m;h++)
          for(k=1;k<=n;k++)
          {
            a=max(sum[i-1][j][h-1][k],sum[i][j-1][h][k-1]);
            b=max(sum[i-1][j][h][k-1],sum[i][j-1][h-1][k]);
            sum[i][j][h][k]=max(a,b)+c[i][j];
            if(i!=h&&j!=k)sum[i][j][h][k]+=c[h][k];
          }
    cout<<sum[m][n][m][n];
    return 0;
}

Pascal :

var
  f:array[-50..101,-50..51,-50..51]of longint;
  a:array[-100..100,-100..100]of longint;
  n,i,j,k,m,maxn,s,minn,xxx:longint;
function max(a,b:longint):longint;
 begin
if a>b then max:=a else max:=b
end;
begin
  //assign(input,'message.in');   reset(input);
  //assign9output,'message.out'); rewrite(output);
  readln(n,m);
  for i:=1 to n do
   for j:=1 to m do read(a[i,j]);      fillchar(f,sizeof(f),0);
  xxx:=m+n-2;
  for k:=2 to xxx do
   begin

     for i:=1 to n do
      for j:=i+1 to n do
        begin
          if abs(j-i) > 1 then
           begin
              f[k,i,j]:=max(f[k-1,i,j],f[k-1,i,j-1]);
              f[k,i,j]:=max(f[k,i,j],f[k-1,i-1,j]);
              f[k,i,j]:=max(f[k,i,j],f[k-1,i-1,j-1]);
              inc(f[k,i,j],a[i,k+1-i]+a[j,k+1-j]);
           end else

           begin
             f[k,i,j]:=max(f[k-1,i,j],f[k-1,i-1,j-1]);
             f[k,i,j]:=max(f[k,i,j],f[k-1,i-1,j]);
              inc(f[k,i,j],a[i,k+1-i]+a[j,k+1-j]);
           end;

        end;
   end;
  writeln(f[xxx,n-1,n]);
//  close(input); rewrite(output);
end.

Java :

import java.util.Scanner;

public class Main {

	static int[][] map;// 好心程度
	static int[][][][] dp;

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int m = sc.nextInt();
		int n = sc.nextInt();
		map = new int[52][52];
		dp = new int[52][52][52][52];
		for (int i = 1; i <= m; i++) {
			for (int j = 1; j <= n; j++) {
				map[i][j] = sc.nextInt();
			}
		}
		int sum = dp(m, n);
		System.out.println(sum);
	}

	static int dp(int m, int n) {
		for (int x1 = 1; x1 <= m; x1++) {
			for (int y1 = 1; y1 <= n; y1++) {
				for (int x2 = 1; x2 <= m; x2++) {
					for (int y2 = 1; y2 <= n; y2++) {
						/*
						 * 
						 * 如果第一个人没有走到最后一行或最后一列，并且两个人没有重复
						 * 因为走到最后一行或最后一列，容易造成第二个人无路可走的情况
						 */
						if ((x1 < m || y1 < n) && x1 == x2 && y1 == y2) {
							continue;
						}
						dp[x1][y1][x2][y2] = Math.max(Math.max(
								dp[x1 - 1][y1][x2 - 1][y2],
								dp[x1 - 1][y1][x2][y2 - 1]), Math.max(
								dp[x1][y1 - 1][x2 - 1][y2],
								dp[x1][y1 - 1][x2][y2 - 1]))
								+ map[x1][y1] + map[x2][y2];
					}
				}
			}
		}
		return dp[m][n][m][n];
	}

}