1047 Student List for Course 25

#include <cstdio>
#include <vector>
#include <algorithm>
#include <cstring>
using namespace std;
const int K = 2510;
const int maxn = 40010;
vector<int> courses[K];
char names[maxn][5];
bool cmp(int a, int b){
    return strcmp(names[a], names[b]) < 0;
}
int main() {
    int N,M;
    scanf("%d%d", &N, &M);
    for(int i = 0; i < N; i++){
        int num;
        scanf("%s %d", names[i], &num);
        for(int j = 0; j < num; j++){
            int id;
            scanf("%d", &id);
            courses[id].push_back(i);
        }
    }
    for(int i = 1; i <= M; i++){
        printf("%d %d\n", i, courses[i].size());
        sort(courses[i].begin(), courses[i].end(), cmp);
        for(int j = 0; j < courses[i].size(); j++){
            printf("%s\n", names[courses[i][j]]);
        }
    }
    return 0;
}