A1047 Student List for Course [unordered_map]

#include<vector>
#include<iostream>
#include<algorithm>
#include<unordered_map>
#include<set>
#include<map>
using namespace std;
int main()
{
	unordered_map<int, vector<string>>Class;
	int n, m, a, j;
	scanf("%d %d", &n, &m);
	for (int i = 0; i < n; i++)
	{	
		string name;
		cin >> name >> a;
		for (int i = 0; i < a; i++)
		{
			scanf("%d", &j);
			Class[j].push_back(name);
		}
	}
	for (int i = 1; i <= m; i++)
	{
		sort(Class[i].begin(), Class[i].end());
		printf("%d %d
", i, Class[i].size());
		for (auto it : Class[i])
		{
			printf("%s
", it.c_str());
		}
	}

}