Thread: Need help

Well, I am a little new at this but I had a similar question about this same context...so I'll give this a shot. I might do more harm than good but here goes....

The function definition:
int Search(struct stutable *T, int id, struct student **stud)

Assuming that the variables
stutable *A, *B; are declared.

when it's called, it's called like this.


Search(A, id, &B) A is the pointer to a structure. id is the numeric student ID number that you are searching your list in hopes of finding a match. You're passing the address of a pointer for B which is your list. (This has something to do with having access to the last node of the linked list. But the **stud is a double dereference. First dereference gets you access to the address of the pointer, the second gets you access to the pointer itself.)

So when you use the pointer in your function you use it like this:
(*stud)

or a practical example would be...
*stud = (*stud)->stu;
...to step through the list.

so as you search through your linear linked list...
first make a copy of the head pointer so you can get back to the beginning of the list.

Then begin to search through each node of the list by stepping through the list in a while loop. You stop searching when you find the end of the list that you are searching through.

in the loop, test for the equality. if(id==(*stud)->stu.ID)
I think that's the correct useage of -> and . if your compiler complains, then I'm at least close.

hope this gives you enough information to ask more questions or to send me flaming mail.

Originally posted by C-dummy
I am quite clear about your explaining. Could anybody know how
to code the Search() function and explain clearly what
struct student **stud mean?

C-dummy

stud is a pointer to a pointer to a struct of type student.

There's some good stuff on linked lists at
http://cslibrary.stanford.edu/105/



This was posted to one of my questions today.
Your example is discussed there.

c-dummy, it seems like you're just having a bit of trouble with your english, because everyone is saying the right stuff. what is your native language?

cdummy,

assuming that Key id is a character string and that Struct B is a struct that looks like this:

struct student{
char* name;
struct* student *NEXT;
};

..and your main() calls the routine like this.
Search(id, listexample); where 'id' is what you are looking for in the linked list and 'listexample' is the linked list
Here is an example of a this search routine involving pointers.

Code:

int Search(Key id, Struct *B){
   B=B->NEXT;  //move in from the (dummy) head node
   while (B->next!=NULL){
      if(strcmp(B->name, id)){
         return 1;
      }
      else
      {
         B=B->NEXT;
      }
   }
   return 0;
}

now, in the case that function call is
Search (id, &listexample);
which is similar to your problem...

This means that you have to double dereference the pointer
in the function definition.
int Search(Key id, Struct **B){
*B=(*B)->NEXT; //move in from the (dummy) head node
while ((*B)->next!=NULL){
if(strcmp((*B)->name, id)){
return 1;
}
else
{
*B=(*B)->NEXT;
}
}
return 0;
}

essentially, I just wrote the essence of your search routine for you.

lastly, if you don't know why the first step I did in the example was to move in one link from the dummy node, then you still have alot to learn about simple lists.