Modify my appending function to be able to append for an empty list as well-CodePudding

How should I modify this function to be able to append from an existing list to a NULL/empty list?

void Appending(Diary *List, Diary *Element) {
    Diary *moving = List;
    if (List == NULL) {
        List = kovetkezo;
    } else { 
        while (moving->NextDiary != NULL)
            moving = moving->NextDiary;
        moving->Nextdiary = Element;
    }
}

CodePudding user response：

To allow appending to an empty list, the list pointer in the caller must be updated.

You must either take a pointer to the List pointer: Appending(&head, element);

// Taking a double pointer to the initial element:
void Appending(Diary **List, Diary *Element) {
    Diary *moving = *List;
    if (moving == NULL) {
        *List = Element;
    } else { 
        while (moving->NextDiary != NULL)
            moving = moving->NextDiary;
        moving->Nextdiary = Element;
    }
}

or you can return the updated List pointer and update the list pointer in the caller by storing the return value into it: head = Appending(head, element);

// Returning an updated pointer to the initial element:
Diary *Appending(Diary *List, Diary *Element) {
    Diary *moving = List;
    if (moving == NULL) {
        List = Element;
    } else { 
        while (moving->NextDiary != NULL)
            moving = moving->NextDiary;
        moving->Nextdiary = Element;
    }
    return List;
}

CodePudding user response：

Declare the function to return the updated list.

Diary* Appending(Diary* List, Diary* Element)
{
    Diary* moving = List;
    if (List == NULL)
    {
        List = kovetkezo;
    }
    else
    { 
        while (moving->NextDiary != NULL)
            moving = moving -> NextDiary;
        moving->Nextdiary = Element;
    }
    return List;
}

The caller then uses:

list = Appending(list, newElement);