Thread: change stack to a queue

Taking my original file stack.c with all the stack functions in it, I need to change so this is a queue file.

What I believe is the only difference is the POP function because in a queue the last item in is the last item out. I know this involves two pointers, but I couldn't follow the example in class. Could someone explain the organization of the POP function?



here's the stack code

Code:

/*****************/
/*  stack.c      */
/****************/

#include <stdlib.h>
#include "stack.h"

struct node {

   int data;
   struct node * next;
};

struct node *first;
int count;

void make_empty()
{
   first = NULL;
   count = 0;
}

int is_empty(void)
{
   return count == 0;
}

int is_full(void)
{
   return 0;
}

void push(int insert_value)
{
   struct node *new_node;

   new_node=malloc(sizeof(struct node));
   if (new_node == NULL)  {
      printf("Error in push:  stack is full.\n");
      exit (EXIT_FAILURE);
   }
   new_node->data = insert_value;
   new_node->next = first;
   first = new_node;
   count++;
}

int pop(void)
{
  struct node * top_node;
  int i;

  if (is_empty())  {
     printf("Error in pop: stack is empty.\n");
     exit (EXIT_FAILURE);
  }

  printf("%d deleted successfully.\n",first->data);
  top_node=first;
  i = first->data;
  first = first->next;
  free(top_node);
  count--;
  return i;
}

void print_list()
{
  struct node *ptr;
  if (first == NULL) {
    printf("List is empty.\n\n");
  }

  else  {
       printf("\n\nHere is your list:  \n");
       for (ptr=first;ptr;ptr=ptr->next)
           printf("%d\n",ptr->data);
       return;
  }
}