51nod 1051 最大子矩阵和

思路：

dp。

实现：

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
typedef long long ll;

int n, m, a[505][505], dp[505];
ll b[505];

ll solve(ll * c)
{
    ll sum = 0, maxnn = 0;
    for (int l = 0; l < m; l++)
    {
        sum += c[l];
        if (sum < 0)
            sum = 0;
        if (sum > maxnn)
            maxnn = sum;
    }
    return maxnn;
}

int main()
{
    cin >> m >> n;
    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++)
            cin >> a[i][j];
    ll maxn = 0;
    for (int i = 0; i < n; i++)
    {
        memset(b, 0, sizeof(b));
        for (int j = i; j < n; j++)
        {
            for (int k = 0; k < m; k++)
            {
                b[k] += a[j][k];
            }
            ll s = solve(b);
            maxn = max(maxn, s);
        }
    }
    cout << maxn << endl;
    return 0;
}