思路：

dp。

实现：

1 #include 
     
       2 #include 
      
        3 #include 
       
         4 #include 
        
          5 using namespace std; 6 typedef long long ll; 7  8 int n, m, a[505][505], dp[505]; 9 ll b[505];10 11 ll solve(ll * c)12 {13     ll sum = 0, maxnn = 0;14     for (int l = 0; l < m; l++)15     {16         sum += c[l];17         if (sum < 0)18             sum = 0;19         if (sum > maxnn)20             maxnn = sum;21     }22     return maxnn;23 }24 25 int main()26 {27     cin >> m >> n;28     for (int i = 0; i < n; i++)29         for (int j = 0; j < m; j++)30             cin >> a[i][j];31     ll maxn = 0;32     for (int i = 0; i < n; i++)33     {34         memset(b, 0, sizeof(b));35         for (int j = i; j < n; j++)36         {37             for (int k = 0; k < m; k++)38             {39                 b[k] += a[j][k];40             }41             ll s = solve(b);42             maxn = max(maxn, s);43         }44     }45     cout << maxn << endl;46     return 0;47 }