Why position 0 in delete node does not work? - c

Question

Im new to c programming. I wanted to create a linked list from a given file and then randomly get a node from linked list then delete that node.
So the code works great but for the position 0 in linked list does not work.
Please help me
here's the code:
typedef struct node{
int *name;
struct node *next;
}node;
delete node:
void deleteNode(node **head_ref, int position){
if(*head_ref == NULL){
return;
}
node * temp = *head_ref;
if(position == 0)
{
*head_ref = (*head_ref)->next;
return;
}
int h;
for(h=0 ; temp!=NULL && h<position-1 ; h++){
temp = temp->next;
}
if(temp == NULL || temp->next == NULL)
return;
node * next = temp->next->next;
free(temp->next);
temp->next = next;}
getting random node:
void RandomFromList(node *head){
// IF list is empty
if (head == NULL){
return -1;
}
word = head->name;
// Iterate from the (k+1)th element to nth element
node *current = head;
int n;
for (n=2; current!=NULL; n++)
{
// change result with probability 1/n
if (rand() % n == 0)
word = current->name;
// Move to next node
current = current->next;
}
sprintf(words , "%s" , word);
deleteNode(&head , search(head , word));
printf("Randomly selected key is %s\n", words);}
and the file Reader:
node* fileReader(FILE *file){
node *t = malloc(sizeof(node));
char TopicName[20];
int fileRead = fscanf(file,"%s",TopicName);
if(fileRead != EOF){
t->name = strdup(TopicName);
tedad++;
t->next = fileReader(file);
}
if(fileRead == EOF) {
return NULL;
}
return t;}
EDIT:
When the code run's and when the position randomly got 0 the 0 position of linked list doesn't delete and continues with that node in linked list.
EDIT2:I changed my delete node and it works well without any problem, thank you guys!
node* deleteNode(node* head, unsigned i){
node* next;
if(head == NULL)
return head;
next = head->next;
return i == 0
? (free(head), next)
: (head->next = delete_at_index(next, i - 1), head);
}

Answer 1

The major logical problem I see with your delete function is that it is void, i.e. it returns nothing. This is fine if the node being deleted is in the middle (or end) of the list, because the head does not change. But for the case of deleting the head, the caller might expect that his reference would then point to the next node (or null, if a list of one element) after making the call. Consider this code:
node* deleteNode (node *head_ref, int position)
{
// passing in a NULL list returns NULL
if (head_ref == NULL) {
{
return NULL;
}
// deleting the first element returns the second element as the new head
node* temp = head_ref;
if (position == 0)
{
node* ret = temp->next;
free(head_ref);
return ret;
}
// otherwise walk down the list to one before the deletion position
for (int h=0; temp != NULL && h < position-1; h++) {
temp = temp->next;
}
// if found, delete the node at the desired position
if (temp != NULL && temp->next == NULL) {
node* next = temp->next->next;
free(temp->next);
temp->next = next;
}
// for cases other than deleting the head, just return the current
// (unmodified) head
return head_ref;
}

Answer 2

This isn't related to your problem, but don't forget to free the memory:
node * temp = *head_ref;
if(position == 0)
{
*head_ref = temp->next;
free(temp); // <--------
return;
}
Also, you already have a pointer (temp) to *head_ref, it looks cleaner to me to just use that pointer instead of dereferencing head_ref again.

Answer 3

void deleteNode(node **head_ref, int pos){
node *del;
for ( ; *head_ref; head_ref = &(*head_ref)->next) {
if (pos-- <= 0) break;
}
if (!*head_ref) return; // Reached end of list: nothing found
del = *head_ref;
*head_ref = del->next;
free(del);
return;
}

Answer 4

If you want to keep deleteNode void, then the problem is with your RandomFromList function. You are just changing the * head that exists in the function body not the pointer you passed to the function, so it's still pointing to the previous node.
It's because that pointers are passed by value (copied) like other things in C.
Try making RandomFromList return the head pointer.
P.s. I think you also have some memory leaks in the delete function.