Calling insert function in c from a header file - c

Question

My professor send me a library to insert,delete and search elements in a linked list:
#include <stdlib.h>
struct NODE
{
char AM[12];
char name[40];
int semester;
struct NODE *head;
struct NODE *next;
struct NODE *prev;
};
void init(struct NODE **head)
{
*head=NULL;
}
struct NODE *Search (struct NODE *head,char CODE[],struct NODE **prev)
{
struct NODE *tmp;
*prev=NULL;
tmp=head;
while (tmp!=NULL && tmp->AM<CODE)
{
*prev=tmp;
tmp=tmp->next;
}
if (tmp==NULL)
return NULL;
if (tmp->AM==CODE)
return tmp;
return NULL;
}
struct NODE *Search2 (struct NODE *head,char name[],struct NODE **prev)
{
struct NODE *tmp;
*prev=NULL;
tmp=head;
while (tmp!=NULL && tmp->name<name)
{
*prev=tmp;
tmp=tmp->next;
}
if (tmp==NULL)
return NULL;
if (tmp->name==name)
return tmp;
return NULL;
}
int Insert (struct NODE **H,struct NODE P)
{
struct NODE *cur,*prev;
cur=Search(*H,P.AM,&prev);
if (cur)
return 0;
cur=(struct NODE *)malloc(sizeof P);
*cur=P;
if (prev==NULL)
{
cur->next=*H;
*H=cur;
}
else
{
cur -> next = prev -> next;
prev -> next = cur;
}
return 1;
}
int Delete (struct NODE **H,char AM[])
{
struct NODE *cur,*prev,*next;
cur=Search(*H,AM,&prev);
if (!cur)
return 0;
if (prev==NULL)
cur=next;
else
prev->next=cur->next;
free(cur);
return 1;
}
void traverse (struct NODE *head)
{
struct NODE *cur;
cur=head;
while (cur)
{
printf ("%p\n",cur);
cur=cur->next;
}
}
Now here is a piece of code from the source file that i created in an attempt to insert an element in the linked list:
case 1:printf ("Input AM,name and semester of student: ");
tmp=(struct NODE *)malloc(sizeof(struct NODE));
if (tmp==NULL)
exit(1);
scanf("%s %s %d",tmp->AM,tmp->name,&tmp->semester);
_flag=Insert(&head,*tmp);
if(_flag)
printf ("Student inserted succesfully!\n");
free(tmp);
break;
When i insert the element i get the "Student inserted succesfully" message,but when i call the search function to find that element,it returns NULL (meaning that the element is not in the list).How should i call the Insert function from the header file? (I assume the problem must be in the Insert function).Also in main() i have declared the following two:
struct NODE *head;
struct NODE *tmp;
Should i change something regarding those two?

Answer 1

I think your problem is in the Search() and Search2() functions, where you've got things like this:
while (tmp!=NULL && tmp->AM<CODE)
and
if (tmp->AM==CODE)
return tmp;
You're comparing the pointers, rather than the contents of the strings. If you want to compare the strings, or find which is first alphabetically, use strcmp().
while (tmp!=NULL && strcmp(tmp->AM, CODE) < 0)
and
if (!strcmp(tmp->AM, CODE))
return tmp;
The same goes for the comparison between tmp->name and name in Search2().