deleting a node in linear single linked list given the start of the list

deleting a node in linear single linked list given the start of the list

I have the following code which deletes a given node from the linear
single linked list. I want to know if we can still improve this program
and does it break anytime
struct node
{
int num;
struct node *next;
} s;
void delete(struct node *first)
{
int flag = 0;
s *ptr, *lastNodePtr = NULL, *deleteNode;
deleteNode = (s*) malloc(sizeof(s));
printf("enter the node value to delete");
scanf_s("%d",&deleteNode->num);
deleteNode->next = NULL;
for (ptr=first;ptr!=NULL;ptr=ptr->next) //at least one element
exist
{
if(deleteNode->num == ptr->num)
{
flag=1;
if(ptr==first) //need to delete at first place
{
free(ptr);
first = null; //i dont think we need to do this as it
points to ptr and ptr is already null.
}
else // need to delete some where middle.it can be last as
well.
{
lastNodePtr->next=ptr->next;
free(ptr);
}
printf("successfully deleted..");
break;
}
lastNodePtr=ptr; // taking note of last node visited..
}
if (flag==0)
{
printf("\n Couldn't find the node");
return;
}
}