mojErweiterung

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

typedef struct Element_s
{
    char name[256];
    //long duration; //Sekunden;
    char interpreteur[256];
    struct Element_s *next;
    struct Element_s *prev;
} Element_t;

void read_in(Element_t *item);
Element_t *allocate();
Element_t *push_back(Element_t *list);
Element_t *find_end(Element_t *list);
void cleanup_list(Element_t **list);
void print_element(Element_t *element);
void print_list(Element_t *list);
void print_list_reverse(Element_t *list);
Element_t *elementAt(Element_t *list, long index);
long elementsCount(Element_t *list);
Element_t *insertFirst(Element_t *list);
Element_t *deleteAt(Element_t *list, long index);
void print_list_random(Element_t *list);


int main()
{
    long i, j;
    Element_t *liste = 0;

    liste = push_back(liste);
    liste = push_back(liste);
    liste = push_back(liste);

    printf("\nListing: ");
    print_list(liste);

    printf("\n\nUmgekehrte Reihenfolge: \n");
    print_list_reverse(liste);

    printf("\nPrint Element at: ");
    scanf("%ld", &i);
    print_element(elementAt(liste, i));

    printf("\nElements count : %ld\n", elementsCount(liste));

    while(getchar() != '\n');
    printf("Insert a song on the first place: -> \n");
    liste = insertFirst(liste);
    print_list(liste);

    printf("\nDelete Element at: ");
    scanf("%ld", &j);
    liste = deleteAt(liste, j);
    print_list(liste);

    printf("\n---------Random list:---------");
    print_list_random(liste);

    cleanup_list(&liste);

    return 0;
}


void read_in(Element_t *item)
{
    printf("Name: ");
    fgets(item->name, 256, stdin);

    printf("Interpreteur: ");
    fgets(item->interpreteur, 256, stdin);
    //while(getchar() != '\n');

}

Element_t *allocate()
{
    Element_t *element = malloc(sizeof(Element_t));

    if(element == 0)
    {
        fprintf(stderr, "Error! No memory available!");
        //return 0;
    }
    else
    {
        read_in(element);
        element->prev = 0;
        element->next = 0;
    }
    return element;
}

Element_t *find_end(Element_t *list)
{
        while(list->next != 0)
            list = list->next;
        return list;
}

Element_t *push_back(Element_t *list)
{
    Element_t *element = allocate();

    if (element == 0)
    {
        fprintf(stderr, "Error: No memory allocated for push_back!\n");
        return list;
    }

    if(list != 0)
    {
        Element_t *end = find_end(list);
        element->prev = end;
        end->next = element;
    }
    else
    {
        list = element;
    }
    return list;
}

void cleanup_list(Element_t **list)
{
    Element_t *s = *list;
    Element_t *t = s;

    while(t != 0)
    {
        t = t->next;
        free(s);
        s = t;
    }
    printf("\nMemory freed.\n");
}

void print_element(Element_t *element)
{
    if(element != 0)
    {
    printf("\nName: %s", element->name);
    printf("Interpreteur: %s", element->interpreteur);
    }
    else
    {printf("\nDie Stelle ist leer!");
    exit(-1);}
}

void print_list(Element_t *list)
{
    long i=0;
    while(list != 0)
    {
        i++;
        printf("\nSong %ld .", i);
        print_element(list);
        list = list->next;
    }

}

void print_list_reverse(Element_t *list)
{
   /* if(list != 0)
    {
        print_list_reverse(list->next);
        print_element(list);
    }
  */long i = 1;
    list = find_end(list);
    while (list != 0)
    {
        printf("\nSong %ld .", i);
        printf("\nName: %s", list->name);
        printf("Interpreteur: %s", list->interpreteur);
        list = list->prev;
        i++;
    }
}

Element_t *elementAt(Element_t *list, long index)
{
    if(list == 0)
    {
        printf("\tSong does not exist.\n");
        return 0;
    }

    long i = 0;

    while (list != 0)
    {
        i++;
        if (index == i)
            return list;
        else
        list = list->next;
    }
    //return list;
}

long elementsCount(Element_t *list)
{
    long i = 0;
    while (list != 0)
    {
        list = list->next;
        i++;
    }
    return i;
}

Element_t *insertFirst(Element_t *list)
{
    Element_t *element = allocate();
    if (element == 0)
    {
        fprintf(stderr, "Error: No memory allocated for insert_fisrt!\n");
        return list;
    }

    if(list == 0)
    {
        list = element;
    }
    else
    {
        element->next = list;
        list->prev = element;
    }
    return element;

}

Element_t *deleteAt(Element_t *list, long index)
{
    //long i = 0;
    list = elementAt(list, index);

    if(list->prev == 0)
        {
            list->next->prev = 0;
            list = list->next;
        }

    else if(list->next == 0)
    {
        list->prev->next = 0;
        while(list->prev != 0)
        {
            list = list->prev;
        }
    }

    else
    {
        list->prev->next = list->next;
        list->next->prev = list->prev;

        while(list->prev != 0)
        {
            list = list->prev;
        }
    }
    return list;
}

void print_list_random(Element_t *list)
{
    if(list != 0)
    {
        if(rand() > RAND_MAX/2 )
        {
            print_list_random(list->next);
            print_element(list);
        }
        else
        {
            print_element(list);
            print_list_random(list->next);
        }
    }
}