简单的DP终于能自己想出来了

#include<bits/stdc++.h>
using namespace std;
const int N = 1010;
int n, m, q;
int a[N][N];
int f[N][N];
int main()
{
    cin >> q;
    while (q--) {
        cin >> n >> m;
        memset(a, 0, sizeof(0));
        memset(f, 0, sizeof(0));
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= m; j++) {
                cin >> a[i][j];
            }
        }
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= m; j++) {
                f[i][j] = max(f[i - 1][j], f[i][j - 1]) + a[i][j];
            }
        }
        cout << f[n][m] << endl;

    }

    return 0;
}