I have a question about linked list

Hello,
I need to write a code in C that make linked list
my professor gave us a three struct
one of them is :

Code:

typedef struct classNode { struct classNode *next; struct genusNode *down; char name[NAME_LENGTH]; double diversity; }classNode;

I start to write the program and i dont know how to write a function that make the linked list of this struct
1) i dont know what i need to send to the function
2) the user need to enter the name and the diversity in the function and after that i dont know what to do with those Parameter (name and diversity) !!!

if someone can help me how to write this function i thank him a lot

P.S

struct classNode *next pointer to the next struct classNode
struct genusNode *down; pointer to struct genusNode

bye,

I understand the data structure as I have used a data structure with next and down pointers myself before. However I don't understand how you want to build this 'tree' (it's not really just a 'list'). Where does that data come from and how do you need to insert it?

Where is the code you're written so far?

this is my code so far

Code:

// Function that make a linked list to the classNode genus !!! classNode *Insert_or_Update_Class(classNode *next,classNode *down,classNode *temp,classNode *head){ // Enter name of class and number diversity and check if its not wrong input!!! do{ printf ("Enter class name:\n"); gets (name); printf ("Enter diversity:\n"); scanf ("%lf",&diversity); gets (check); // here i send the input to a function that check if the input is good !!! input_check=check_input_class(diversity,name,check); }while (!input_check); // start to create or update the class !!! temp=(classNode*)malloc(sizeof(classNode)); if (!temp) return NULL; temp->next=head; head=temp; strcpy(temp->name,name); temp->diversity=diversity; temp->down=NULL; temp->next=NULL; return head; }//End create_or_update_class//

i dont know if i send the right parameter to the functiovn

Don't use gets - it's dangerous. Use fgets instead.

my problem is not the gets
my problem is that i dont know if what i send to the function is right (is run good but when i want to create another struct the first is not exist so what i'm doing wrong ????)

bye

Quote:

Originally Posted by Tzahi

my problem is not the gets

Typically, we teach and correct safe and portable code and gets isn't safe. So you should change your application to use fgets instead.

Just as an fyi, to change what a pointer points to, you can't pass in the pointer itself. You have to pass a pointer to the pointer. I haven't looked thoroughly through your code, but you are altering temp in your function. You also seem to move it around so head points to it as well, and a few more shell iteration. This won't change the value of what the pointers point to in the original calling function.

Quote:

Originally Posted by Tzahi

this is my code so far

Code:

// Function that make a linked list to the classNode genus !!! classNode *Insert_or_Update_Class(classNode *next,classNode *down,classNode *temp,classNode *head)

i dont know if i send the right parameter to the function

You're suspicions are correct. You're sending too many parameters to that function. You'll notice that you're not using next or down. I also noticed that you're using a global called 'name' that should probably be a local, as should temp I suspect. You know how to declare locals right? Just like a global, but inside the function.
The only things left that we need to know are, how is this function called, and when do you want the node to be inserted in the down list instead of the next list?

Quote:

Originally Posted by Elysia

Typically, we teach and correct safe and portable code and gets isn't safe. So you should change your application to use fgets instead.

It's not important for the OP to change to fgets at the moment, he or she can read up about it in their own time afterwards. You make it seem as though you wont help until the OP does exactly what you want with the code first. Typically we actually try and help the poster, though we may throw in a few safety or performance tips along the way.
I'm sure you'd produce a similiar response if you posted some code only for someone to immediately post comments we know you weren't after. E.g. 'Foo' isn't a good name for a class.

Indeed. Well, if it sounds that I'm implying that I should demand it changes before helping further, then let me add that it is not so.
The code is a mystery to me, though, so I'm not helping very much. I've been staying away from the subject since I don't have a good enough understanding to suggest corrections.

Yes, this is a tricky one to help with, I'll admit. I've realised that there are still many more unanswered questions. For example, do you want to insert at the front of the list, at the end, or in sorted order most often somewhere in the middle?
Same question for the down list.
Next, is it valid for head->down->next to be non-null? In other words is this really like a tree, or is it more like a list of lists.

We really can't tell what you want to do. Perhaps the problems comes from you not knowing what you need to do either?! Lots more information required please!

first of all. which type of a linked list are you trying to write a code for???
>singly linked
>doubly linked
??
if it is a singly linked... then
where are insertions done and where are deletions>?
is it a lifo or fifo???????
if you are trying to do a lifo
one pointer at the head may be sufficient...

if u are doing a fifo you might need a front and rear pointer....

can you explain a bit in detail....

and why do you want a insert function pointer ..
you can as well declare it as

Code:

void insert(void) { classnode *nu; //take inputs here nu->nxt=head; head=nu; }

this would suffice....
just declare head as global and initialize it to NULL