1047 Student List for Course (25point(s)) 需要二刷 *需要重点注意关于性能得问题

#include<iostream>
#include<stdlib.h>
#include<stdio.h>
#include<vector> 
#include<string>
#include<math.h>
#include<algorithm>
#include<cstring>
#include<map>
#include<queue>
using namespace std;

const int maxn = 40010;
int n, k;

vector<int> per[maxn];
char stu[maxn][5];

bool cmp(int a, int b) {
    return strcmp(stu[a],stu[b])<0;
}

int main() {
    scanf("%d %d", &n, &k);
    string s;
    int a,b;
    for (int i = 0; i < n; i++) {
        scanf("%s %d", stu[i], &a);
        for (int j = 0; j < a; j++) {
            scanf("%d",&b);
            per[b].push_back(i);
        }
    }
    for (int i = 1; i <= k; i++) {
        printf("%d %d\n", i, per[i].size());
        sort(per[i].begin(), per[i].end(), cmp);
        for (int j = 0; j < per[i].size(); j++) {
            printf("%s\n", stu[per[i][j]]);
        }
    }
    return 0;
}