PAT 1047 Student List for Course (25分)

#include <iostream>
#include <algorithm>
#include <vector>
#include <cstring>

using namespace std;
char name[40010][5];
bool cmp (int a,int b){
    return strcmp(name[a],name[b])<0;

}
vector<int> v[2510];

int main(){
    int n,k;
    cin>>n>>k;
    int num,course;
    for(int i=0;i<n;i++){
        scanf("%s%d",name[i],&num);
        for(int j=0;j<num;j++){
            scanf("%d",&course);
            v[course].push_back(i);
        }
    }
    for(int i=1;i<k+1;i++){
        sort(v[i].begin(),v[i].end(),cmp);
        printf("%d %d\n",i,v[i].size());
        for(int j=0;j<v[i].size();j++){
            printf("%s\n",name[v[i][j]]);
        }

    }
    return 0;
}