解题思路

代码

原始做法 O(N^3)

#include <iostream>

using namespace std;

const int N = 1010;
int v[N], w[N], f[N][N];

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

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

    return 0;
}

优化时间 O(N^2)

#include <iostream>

using namespace std;

const int N = 1010;
int v[N], w[N], f[N][N];

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

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

    return 0;
}

优化空间

#include <iostream>

using namespace std;

const int N = 1010;
int v[N], w[N], f[N];

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

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

    return 0;
}