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

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

struct node *add_to_front(struct node *list, int v);
struct node *remove_from_back(struct node *list);
void print_list(struct node *list);

int main() {
   struct node *front = NULL;
   int value;
   while (1) {
      printf("Enter a number: ");
      int rtn = scanf("%d", &value);
      if (rtn != 1) 
         break;
      else
         front = add_to_front(front, value);
   }

   print_list(front);

   front = remove_from_back(front);
   print_list(front);

   front = remove_from_back(front);
   print_list(front);

   front = remove_from_back(front);
   print_list(front);

   return 0;
}

struct node *add_to_front(struct node *list, int v)
{
   struct node *new_node = malloc(sizeof(struct node));
   if (new_node == NULL) {
      printf("Error: malloc failed in add_to_front\n");
      exit(EXIT_FAILURE);
   }

   new_node->value = v;
   new_node->next = list;
   return new_node;
}

struct node *remove_from_back(struct node *list)
{
   if (list == NULL)
      return list; //empty list

   struct node *cur, *prev;

   for (cur = list, prev = NULL;
        cur->next != NULL;
        prev = cur, cur = cur->next) 
      ;

   if (prev == NULL) //list has only one node
      list = list->next; 
   else 
      prev->next = cur->next; //point to NULL
   free(cur);
   return list;
}

void print_list(struct node *list) 
{
   for (; list != NULL; list = list->next) {
      printf("%d ", list->value);
   }
   printf("\n");
}