矩陣中最大的二維矩陣

5 3

int fun(vector<vector<int> > &a)
{
	int m = a.size();
	int n = a[0].size();

	int buf[m][n];
	for (int i = 1; i < m; i++)
	{
		buf[i][1] = a[i-1][0] + a[i-1][1] + a[i][0] + a[i][1];
		for (int j = 2; j < n; j++)
		{
			buf[i][j] = buf[i][j-1] + a[i-1][j] + a[i][j];
		}
	}

	int result = INT_MIN;
	for (int i = 1; i < m; i++)
	{
		if (buf[i][1] > result)
		{
			result = buf[i][1];
		}

		for (int j = 2; j < n; j++)
		{
			int temp = buf[i][j] - buf[i][j-2];
			if (temp > result)
			{
				result = temp;
			}
		}
	}

	return result;
}