解法一：Map+Set

用 Map 和 Set 存储每个学生的选课信息， STL 的 Set 是有序的。

#include <bits/stdc++.h>
using namespace std;
// (name, set<course index>)
map<string, set<int>> stuMap;
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int N, K;
    cin >> N >> K;
    int index, num;
    string stuName;
    for (int i = 0; i < K; ++i) {
        cin >> index >> num;
        for (int j = 0; j < num; ++j) {
            cin >> stuName;
            auto res = stuMap.find(stuName);
            if (res == stuMap.end()) {
                stuMap.emplace(stuName, set<int>{index});
            } else {
                res->second.insert(index);
            }
        }
    }
    for (int i = 0; i < N; ++i) {
        cin >> stuName;
        cout << stuName << " ";
        auto res = stuMap.find(stuName);
        if (res == stuMap.end()) {
            cout << "0\n";
        } else {
            cout << res->second.size();
            for (auto e:res->second) {
                cout << " " << e;
            }
            cout << '\n';
        }
    }
}