Thread: SIngle Linked List processing

I wrote two functions to delete first list item. One with argument (a pointer that shows the head of the list. i wanted to choose which list through it's header, if i had more than one) and one without argument (head of the list is global pointer as you can see in code). The problem is that delete_first1() is working right (i use the print_list() to see what is happening) but delete_first2(struct node *ptr) is not. Can someone see why?

Code:

#include <stdio.h>
#include <stdlib.h>

struct node
{
    int data;
    struct node *next;
};

struct node *head=NULL;
struct node *current=NULL;

void insert_first(int number)
{
    struct node *link =  (struct node *)malloc(sizeof(struct node)); //create the new node dynamically
    link->data = number; //entering data field
    link->next = head; //next field points where head was pointing
    head = link;//head points to the new node
}


void print_list()
{
    struct node *ptr=head; //a pointer shows to head of list
    while(1)
    {
        if(ptr==NULL) break;
        printf("%d ",ptr->data); //print what you see
        ptr=ptr->next;//points to next node
    }
}

struct node *delete_first1()
{
    if(head==NULL)return NULL;

    struct node *temptr=head;
    head=head->next;

    return temptr;
}

struct node *delete_first2(struct node *ptr)
{
    if(ptr==NULL)return NULL;

    struct node *temptr=ptr;
    ptr=ptr->next;

    return temptr;
}

int isEmpty(struct node *ptr)
{
    if(ptr==NULL)return 1;
    return 0;    
}

struct node *search(struct node *ptr, int k)
{
    while(ptr!=NULL)
    {
        if(ptr->data==k)
            return ptr;
        ptr=ptr->next;
    }
    return NULL;
}


int main()
{
    int a1=11,a2=12,a3=13,a4=14;

    
    insert_first(a1);
    insert_first(a2);
    insert_first(a3);
    insert_first(a4);

    print_list();
    delete_first2(head);
    //delete_first1();
    print_list();
    
    return 0;
}