题解 | 【模板】01背包（计数）

#include <iostream>
#include <cstring>

using namespace std;

const int N = 1e4 + 10;
const int M = 1e9 + 7;
int v[N], w[N];

int f[N];
int st[N];

int main() {
    int t;
    cin >> t;
    while (t--) {
        int n, m;
        cin >> n >> m;
        for (int i = 1; i <= n; i++) {
            cin >> v[i] >> w[i];
        }
        memset(f, 0, sizeof f);
        for (int i = 0; i <= m; i++) st[i] = 1;
        for (int i = 1; i <= n; i++) {
            for (int j = m; j >= v[i]; j--) {
                if (f[j] == f[j - v[i]] + w[i]) {
                    st[j] = (st[j] + st[j - v[i]]) % M;
                } else if (f[j] < f[j - v[i]] + w[i]) {
                    f[j] = f[j - v[i]] + w[i];
                    st[j] = st[j - v[i]] % M;
                }
            }
        }
        cout << st[m] << "\n";
    }
}
// 64 位输出请用 printf("%lld")