C :

#include<stdio.h>

const int N=100;

int maxsum(int m,int n,int mat[][N])
{
	int matsum[N][N+1],ret,sum,i,j,k;
	for(i=0;i<m;i++)
		for(matsum[i][j=0]=0;j<n;j++)
			matsum[i][j+1]=matsum[i][j]+mat[i][j];
	for(ret=mat[0][j=0];j<n;j++)
		for(k=j;k<n;k++)
			for(sum=0,i=0;i<m;i++)
			{
				sum=(sum>0?sum:0)+matsum[i][k+1]-matsum[i][j];
				ret=(sum>ret?sum:ret);
			}
	return ret;
}

int main()
{
	int n,i,j,g[N][N];
	while(scanf("%d",&n)!=EOF)
	{
		for(i=0;i<n;i++)
			for(j=0;j<n;j++)
				scanf("%d",&g[i][j]);
		printf("%d\n",maxsum(n,n,g));
	}
	return 0;
}

C++ :

#include<stdio.h>

const int N=100;

int maxsum(int m,int n,int mat[][N])
{
	int matsum[N][N+1],ret,sum,i,j,k;
	for(i=0;i<m;i++)
		for(matsum[i][j=0]=0;j<n;j++)
			matsum[i][j+1]=matsum[i][j]+mat[i][j];
	for(ret=mat[0][j=0];j<n;j++)
		for(k=j;k<n;k++)
			for(sum=0,i=0;i<m;i++)
			{
				sum=(sum>0?sum:0)+matsum[i][k+1]-matsum[i][j];
				ret=(sum>ret?sum:ret);
			}
	return ret;
}

int main()
{
	int n,i,j,g[N][N];
	while(scanf("%d",&n)!=EOF)
	{
		for(i=0;i<n;i++)
			for(j=0;j<n;j++)
				scanf("%d",&g[i][j]);
		printf("%d\n",maxsum(n,n,g));
	}
	return 0;
}

Java :

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		for (; sc.hasNext();) {
			int n = sc.nextInt();
			int[][] array = new int[n][n];
			for (int i = 0; i < n; i++) {
				for (int j = 0; j < n; j++) {
					array[i][j] = sc.nextInt();
				}
			}
			System.out.println(maxSubMatrixSum(array));
		}
		sc.close();
	}

	private static int maxSubMatrixSum(int[][] mat) {
		int ret, sum, i, k;
		int j = 0;
		int[][] matsum = new int[mat.length][mat.length + 1];
		
		for (i = 0; i < mat.length; i++)
			for (j = 0,matsum[i][j] = 0; j < mat.length; j++){
				matsum[i][j + 1] = matsum[i][j] + mat[i][j];
			}
		
		for (j = 0,ret = mat[0][0]; j < mat.length; j++)
			for (k = j; k < mat.length; k++)
				for (sum = 0, i = 0; i < mat.length; i++) {
					sum = (sum > 0 ? sum : 0) + matsum[i][k + 1] - matsum[i][j];
					ret = (sum > ret ? sum : ret);
				}
		return ret;
	}

}