Thread: Multiple linked lists

How do we keep track of multiple linked lists?

Suppose I create a linked list that stores information about cars and another about motorcycles.

I don't understand how I can do that without declaring so many structs

By too many, I assume you mean a new node type for every struct type?
In that case, void pointers or unions for the win...

Code:

struct motorcycle_t
{
    int cc;     /* some random data */
};

struct car_t
{
    int seats;  /* whatever */
};

enum vehicleType_t
{
    VT_CAR = 0,
    VT_MOTORCYCLE
};

struct listNodeWithUnions_t
{
    union
    {
        struct car_t car;
        struct motorcycle_t motorcycle;
    } data;
    enum vehicleType_t type;

    struct listNode_t * next;
    struct listNode_t * previous;
};

/* OR */

struct listNodeWithVoidPointers_t
{
    void * data;
    enum vehicleType_t type;

    struct listNode_t * next;
    struct listNode_t * previous;
};

/* ... */

Personally I'd use void pointers and cast back... look at how linked-lists are implemented in glib (Gtk+) and you should get it. Link: http://library.gnome.org/devel/glib/...ked-Lists.html

Uh oh, that looks a bit tougher than I expected, but hey, thanks for the link! There are some useful list operations in there that I needed to know.

Yes, once you start using glib you don't want to stop

Originally Posted by zacs7

Yes, once you start using glib you don't want to stop

Haha, sounds like you are rather ambivalent towards all of it

> How do we keep track of multiple linked lists?
Arrays, trees, other lists, etc etc

Code:

enum { CAR, MBIKE, MAXTYPE };
listtype *lists[MAXTYPE];

Originally Posted by Salem

> How do we keep track of multiple linked lists?
Arrays, trees, other lists, etc etc

Code:

enum { CAR, MBIKE, MAXTYPE };
listtype *lists[MAXTYPE];

What is listtype *lists[MAXTYPE] ?

That looks like something I've been looking for in google

Can I do something like this:

Code:

typedef struct numbers NS;
typedef struct list LS;

struct list {
  LS *next;
};

struct numbers {
  NS *array;
  int mean;
  int mode;
  int average;
};

What I'm essentially trying to do is make several lists of numbers, and then have a pointer to these different lists to keep track of them. Would the struct list be able to do that?

> What is listtype *lists[MAXTYPE]
An array of pointers to listtype

listtype being whatever you want it to be.