HW2_stud

#include <cstdio>
#include <cstdlib>
#include <cmath>

struct stud
{
    int id;
    char name[33];
    int mark;
};

struct Node
{
    Node * next;
    Node * prev;
    stud * key;
};

struct List
{
    Node * first;
    Node * last;
};

void swap(Node * a)
{
    Node * b = a->next;
    a->next = a->prev;
    a->prev = b;
}

int push(List* l, stud* a)
{
    Node * q = (Node *)malloc(sizeof(Node));
    if (!q)
        return 0;
    q->key = a;
    l->last->prev->next = q;
    q->prev = l->last->prev;
    q->next = l->last;
    l->last->prev = q;
    return 1;
}


List* list_new()
{
    List* a = (List*)malloc(sizeof(List));
    Node* q = (Node*)malloc(sizeof(Node));
    Node* w = (Node*)malloc(sizeof(Node));
    q->prev = NULL;
    w->next = NULL;
    q->next = w;
    w->prev = q;
    a->first = q;
    a->last = w;
    return a;
}

void list_delete(List* l)
{
    Node* a = l->first;
    Node* b;
    while (a != NULL)
    {
        b = a->next;
        free(a);
        a = b;
    }
    free(l);
}


int main()
{
    int n = 0, k = 0;
    scanf("%i", &n);
    stud* arr = (stud*)malloc(n*sizeof(stud));
    List** mas = (List**)malloc(4 * sizeof(List*));
    for (int i = 0; i < 4; i++)
        mas[i] = list_new();
    int from = 0, to = 0;
    for (int i = 0; i < n; ++i)
    {
        scanf("%i%n%s%n", &arr[i].id, &from, arr[i].name, &to);
        scanf("%s%i", arr[i].name + to - from, &arr[i].mark);
        arr[i].name[to - from - 1] = ' ';
        push(mas[arr[i].mark - 2], &arr[i]);
    }
    for (int j = 0; j < 4; j++)
    {
        for (Node* i = mas[j]->first->next; i->next; i = i->next)
            printf("%i %s %i\n", i->key->id, i->key->name, i->key->mark);
    }
    return 0;
}