Deletion in a Linked List | C Program

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

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

int calcSize (struct Node *node)
{
  int size = 0;

  while (node != NULL)
    {
      node = node->next;
      size++;
    }
  return size;
}

void delete (struct Node **head, int pos)
{
  struct Node *temp = *head;
  struct Node *previous;

  //if the head node itself needs to be deleted
  int size = calcSize (*head);

  if (pos < 1 || pos > size)
    {
      printf ("Enter valid position\n");

      return;
    }

  if (pos == 1)
    {
      //Case 1 head becomes 30
      *head = temp->next;	//changing head to next in the list
      printf ("Value %d, deleted \n", temp->data);

      //case 1: 22 deleted and freed
      free (temp);
      return;
    }

  //run until we find the value to be deleted in the list
  while (--pos)
    {
      //store previous link node as we need to change its next val
      previous = temp;
      temp = temp->next;
    }


  // Case 2: (24)->next = 16 (as 20->next = 16) 
  // Case 3: (16)->next = NULL (as 12->next = NULL)
  previous->next = temp->next;
  printf ("Value %d, deleted \n", temp->data);

  free (temp);
  //case 2: 20 deleted and freed
  //case 3: 12 deleted and freed
}

void display (struct Node *node)
{

  //as linked list will end when Node is Null
  while (node != NULL)
    {
      printf ("%d ", node->data);
      node = node->next;
    }
  printf ("\n\n");
}

int main ()
{
  //creating 4 pointers of type struct Node
  //So these can point to address of struct type variable
  struct Node *head = NULL;
  struct Node *node2 = NULL;
  struct Node *node3 = NULL;
  struct Node *node4 = NULL;
  struct Node *node5 = NULL;
  struct Node *node6 = NULL;

  // allocate 3 nodes in the heap 
  head = (struct Node *) malloc (sizeof (struct Node));
  node2 = (struct Node *) malloc (sizeof (struct Node));
  node3 = (struct Node *) malloc (sizeof (struct Node));
  node4 = (struct Node *) malloc (sizeof (struct Node));
  node5 = (struct Node *) malloc (sizeof (struct Node));
  node6 = (struct Node *) malloc (sizeof (struct Node));


  head->data = 22;		// data set for head node 
  head->next = node2;		// next pointer assigned to address of node2 

  node2->data = 30;
  node2->next = node3;

  node3->data = 24;
  node3->next = node4;

  node4->data = 20;
  node4->next = node5;

  node5->data = 16;
  node5->next = node6;

  node6->data = 12;
  node6->next = NULL;

  /*No need for & i.e. address as we do not
     need to change head address
   */
  printf ("Linked List Before Operations : ");
  display (head);

  //deleting first occurance of a value in linked list
  delete (&head, 1);
  delete (&head, 3);
  delete (&head, 4);

  printf ("Linked List After Operations : ");
  display (head);

  delete (&head, -2);		// not valid as pos negative
  delete (&head, 10);		// not valid as breaches size of Linked List
  printf ("Linked List After Operations : ");
  display (head);

  return 0;
}