解题思路

分组背包就是扩展了的 01 背包，状态转移与 01 一致。只是拓展了分组内物品的枚举
不做赘述，01 背包

代码

原始做法

#include <iostream>

using namespace std;

const int N = 110;
int v[N][N], w[N][N], s[N], f[N][N];

int main() {
    int n, m;
    cin >> n >> m;
    for (int i = 1; i <= n; i++) {
        cin >> s[i];
        for (int j = 1; j <= s[i]; j++) cin >> v[i][j] >> w[i][j];
    }

    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            f[i][j] = f[i - 1][j];
            for (int k = 1; k <= s[i]; k++) {
                if (j >= v[i][k]) f[i][j] = max(f[i][j], f[i - 1][j - v[i][k]] + w[i][k]);
            }
        }
    }
    cout << f[n][m] << endl;

    return 0;
}

优化后

#include <iostream>

using namespace std;

const int N = 110;
int v[N][N], w[N][N], s[N], f[N];

int main() {
    int n, m;
    cin >> n >> m;
    for (int i = 1; i <= n; i++) {
        cin >> s[i];
        for (int j = 1; j <= s[i]; j++) cin >> v[i][j] >> w[i][j];
    }

    for (int i = 1; i <= n; i++) {
        for (int j = m; j >= 0; j--) {
            for (int k = 1; k <= s[i]; k++) {
                if (j >= v[i][k]) f[j] = max(f[j], f[j - v[i][k]] + w[i][k]);
            }
        }
    }
    cout << f[m] << endl;

    return 0;
}