C :

#include<stdio.h>
#include<string.h>
#include <stdlib.h>

#define MaxName 4
#define MaxC 20

typedef  struct  ListNode  *List;
struct ListNode {
	char Name[MaxName+1];
	List Next;
};

struct StudentNode {
	char Name[MaxName+1];
	int nC;
	int C[MaxC];
} *Student;

struct CourseNode {
	int Counter;
	List Ptr;
} *Course;

int CmpName(const void *a, const void *b) {
   return strcmp(((const struct StudentNode*)a)->Name, ((const struct StudentNode*)b)->Name);
}

void Read_and_Sort( int *N, int *K )
{
	int i, j;

	scanf("%d %d\n", N, K);
	Student = malloc( sizeof( struct StudentNode ) * (*N) );
	Course = malloc( sizeof( struct CourseNode ) * (*K) );
	for (i=0; i<(*K); i++) {
		Course[i].Counter = 0;
		Course[i].Ptr = NULL;
	}
	for (i=0; i<(*N); i++) {
		scanf("%s %d", Student[i].Name, &Student[i].nC);
		for (j=0; j<Student[i].nC; j++)
			scanf("%d", &Student[i].C[j]);
	}

	qsort(Student, (*N), sizeof(struct StudentNode), CmpName);
}

List NewNode( char *name )
{
	List temp;

	temp = (List)malloc(sizeof(struct ListNode));
	strcpy(temp->Name, name);
	temp->Next = NULL;

	return temp;
}

void InsertCourse( int N, int K )
{
	List Node;
	int i, j, CourseIndex;

	for (i=N-1; i>=0; i--)
		for (j=Student[i].nC-1; j>=0; j--) {
			CourseIndex = Student[i].C[j]-1;
			Node = NewNode(Student[i].Name);
			Node->Next = Course[CourseIndex].Ptr;
			Course[CourseIndex].Ptr = Node;
			Course[CourseIndex].Counter ++;
		}
}

void Output( int K )
{
	List Ptr;
	int i;

	for (i=0; i<K; i++) {
		printf("%d %d\n", i+1, Course[i].Counter);
		for (Ptr = Course[i].Ptr; Ptr; Ptr = Ptr->Next)
			printf("%s\n", Ptr->Name);
	}
}

int main()
{
	int N, K;

	Read_and_Sort( &N, &K );
	InsertCourse( N, K );
	Output( K );

	return 0;
}

C++ :

#include<cstdio>
#include<algorithm>
#include<vector>
using namespace std;
const int MAX=2510;
vector<int> course[MAX];
//string to number 
int S2N(char str [])
{
	int sum=0;
	for(int i=0;i<3;i++)
	{
		sum=sum*26+str[i]-'A';
	}
	sum=sum*10+str[3]-'0';
	return sum;
}
void N2S(int num,char str[])
{
	str[4]='\0';
	str[3]=num%10+'0';
	num/=10;
	for(int i=2;i>=0;i--)
	{
		str[i]=num%26+'A';
		num/=26;
	}
}
 
int main(int argc, char *argv[])
{
	int N,M;
	scanf("%d%d",&N,&M);
	for(int i=0;i<N;i++)
	{
		char temp[6];
		scanf("%s",temp);
		int index=S2N(temp);
		int count;
		scanf("%d",&count);
		for(int j=0;j<count;j++)
		{
			int num;
			scanf("%d",&num); 
			course[num].push_back(index);
		}	
	}
	for(int i=1;i<=M;i++)
	{
		sort(course[i].begin(),course[i].end());
		printf("%d %d\n",i,course[i].size());
		for(int j=0;j<course[i].size();j++)
		{
			char temp[6];
			N2S(course[i][j],temp);
			printf("%s\n",temp);
			
		}
	}
	
	
	return 0;
}