HashIndex

So i have to write this function that creates a node to hold a student record specified by siid(student_id), lastname, firstname and gpa. After creating the new node i have to insert it to the proper list in the hash table pointed by hashtable. The memory of the new node is dynamically allocated. my question is: Two students cannot have the same student_id , so if the inserted record has the same student_id with an existing record in the list my program should print to the standard output:

insertion failed: student_id xxxxxx already exists

where xxxxxx is the student_id value. my second question: If the insertion of a record is successful it should print:
.
record xxxxx inserted

this is what i have so far:

Code:

void insertRecord(Student **hashtable, unsigned int sid, char *lastname, char *firstname, float gpa); 
{                
        
        Student *p, *head;
        p=(student *) malloc(sizeof(student));
        
        int i;
        
        Student *s;/*node*/
        
        if (s==NULL)
        {
            s->student_id =sid;
            strcpy(s->firstname,firstname);/*copying first and lastname to s*/
            strcpy(s->lastname,lastname);
            s->gpa=gpa;
            hashtable[sid%M] = s;
        }
            
        else
        {/*s != NULL;*/
             s = s-> next;
             s->student_id=sid;
            
        }
        if (student_id = s)
        {
            printf("insertion failed: student_id %d already exists\n", sid);
        }
        printf("record %d inserted", sid);

1. Use code tags.
2. Why are you checking s when you haven't actually done anything with it? What does it matter if it's NULL or not -- you haven't assigned anything to it, so whatever it has is completely irrelevant.
3. If it was NULL, you immediately try to use it. That's bad.
4. Your last if check uses = instead of == to test for equality.
5. You dupe posted. Just press submit once.

Quzah.

i actually have the main function that tests the program when it is done. i use s as a pointer because i have to go through the hashtable.

quzah in point 2 is talking about this:

Code:

Student *s;/*node*/

if (s==NULL)
{
s->student_id =sid;

You use s without initializing it. That's bad. Then you go on to dereference s if it's NULL. That's bad too.