Question

As always being this problem comes from a book’s exercises.
Neither I am not studying data structures, nor the book is about that.
But, there is a chapter that is “Dynamic Data Structures”. I’ve already finished this chapter.

But, I have problem with insertion. In my opinion, my function works correctly, except that it makes duplicate nodes.

I made a precaution for that but it doesn’t work. Anyway, please forgive me because of my silly mistakes.
OK, Here my structure types for name lists.

typedef struct name_node_s {
char name[11];
struct name_node_s *restp;
}name_node_t;

typedef struct {
    name_node_t *headp;
    int size;
}name_list_t;

place_first function:

name_node_t *
place_first(name_list_t *old_listp, char name[11])
{
    name_list_t *new_listp, *cur_listp;
    name_node_t *new_nodep, *temp_nodep;
    temp_nodep = (name_node_t *)malloc(sizeof (name_node_t));
    new_listp = (name_list_t *)malloc(sizeof (name_list_t));
    cur_listp = (name_list_t *)malloc(sizeof (name_list_t));
    new_nodep = (name_node_t *)malloc(sizeof (name_node_t));
    cur_listp->headp = old_listp->headp;
    temp_nodep = old_listp->headp;
    new_listp = old_listp;
    if ( old_listp->headp->name != name ){ // My first precaution for duplication
        while(cur_listp->headp->restp != NULL && cur_listp->headp->name != name) // My second precaution for duplication
        {
            if (old_listp->headp == NULL){
                strcpy(new_listp->headp->name, name);
                new_listp->headp->restp = NULL;
            }
            else if (old_listp->headp->name != name) { // Third one.
                strcpy(new_nodep->name, name);
                new_nodep->restp = NULL;
                new_listp->headp = new_nodep;
                new_listp->headp->restp = temp_nodep;
                ++(old_listp->size);
            }
        cur_listp->headp = cur_listp->headp->restp;
        }
    }
    else{
        new_listp->headp = old_listp->headp;
    }
    return(new_listp->headp);
}

I call that function like this;

listp->headp = place_first(listp, "Mustafa");
listp->headp = place_first(listp, "Mustafa");

My output like this:
__Mustafa
__Mustafa
__Ataturk
__Ali
__Eisenhower
__Kennedy
Thanks for advance…

Answer 1

Here

if ( old_listp->headp->name != name ){

you are comparing pointers, not the contents, you want

if (strcmp(old_listp->headp->name,name)){

The same applies to the other checks.