HW2_listDanila

#include <cstdio>
#include <cstdlib>
#define _CRT_SECURE_NO_WARNINGS

struct Node
{
    Node * next;
    Node * prev;
    int 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, int 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;
}

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

int shift(List* l, int* q)
{
    Node* a = l->first->next;
    *q = l->first->next->key;
    l->first->next->next->prev = l->first;
    l->first->next = l->first->next->next;
    free(a);
    return 1;
}

int pop(List* l, int* q)
{
    Node* a = l->last->prev;
    *q = l->last->prev->key;
    l->last->prev->prev->next = l->last;
    l->last->prev = l->last->prev->prev;
    free(a);
    return 1;
}

int reverse(List* l)
{
    Node* a = l->first;
    Node* b;
    while (a != NULL)
    {
        swap(a);
        a = a->prev;
    }
    b = l->first;
    l->first = l->last;
    l->last = b;
    return 1;
}

List* list_new()
{
    List* a = (List*)malloc(sizeof(List));
    Node* q = (Node*)malloc(sizeof(Node));
    Node* w = (Node*)malloc(sizeof(Node));
    q->key = 0;
    w->key = 0;
    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()
{
    List* l = list_new();
    int q = 3, w = 5;
    push(l, q);
    for (Node* i = l->first; i; i = i->next)
        printf("%i ", i->key);
    printf("\n");
    unshift(l, w);
    for (Node* i = l->first; i; i = i->next)
        printf("%i ", i->key);
    printf("\n");
    reverse(l);
    for (Node* i = l->first; i; i = i->next)
        printf("%i ", i->key);
    printf("\n");
    pop(l, &q);
    for (Node* i = l->first; i; i = i->next)
        printf("%i ", i->key);
    printf("\n");
    shift(l, &w);
    for (Node* i = l->first; i; i = i->next)
        printf("%i ", i->key);
    printf("\n");
    list_delete(l);
    return 0;
}