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

struct List       // This is the List class definition in C
{
   int          value;
   struct List *next;
};


struct List *insert( struct List *head, struct List *e );
struct List *delete (struct List *h);
void print(struct List *h);   // We must declare print to avoid compile error


void main(int argc, char *argv[])
{  
   struct List *head = NULL;   // Nul pointer NULL instead of null
   struct List *p;
   
   for ( int i = 0; i < 10; i++ )
   {
      p = malloc( sizeof(struct List) );
      p->value = i;
      head = insert(head, p);       // Insert p in head
      print(head);
   }

   for ( int i = 0; i < 10; i++ )
   {
      head = delete(head);       // Insert p in head
      print(head);
   }
}

struct List *insert( struct List *head, struct List *e )
{
   /* --------------------------------------------
       Base case: insert at the tail of an empty
      -------------------------------------------- */
   if ( head == NULL )
   {
      e->next = NULL;   // Mark e as the last list elem
      return(e);         // e is the first list elem !
   }
   else
   {
      /* ===========================================================
         Solve the problem USING the solution of a smaller problem
         =========================================================== */
      head->next = insert( head->next, e ); // Link directly to helpSol

      return head;             // Return MY solution
   }
}

/* ====================================================
   delete(h): delete the LAST elem from the list h
              return new list
   ==================================================== */
struct List *delete (struct List *h)
{
   if ( h == NULL )
      return NULL;    // deleting from empty list: returns an empty list
   else if ( h->next == NULL )
   {  // Delete from list with ONLY 1 element
      free(h);        // De-allocate deleted element
      return NULL;
   }
   else
   { 
      struct List * helpSol;

      helpSol = delete( h->next ); 
      h->next = helpSol;
      return(h);
   }
}

// Print the list
void print(struct List *h)
{
   while (h != NULL)
   {
      printf("%d ", h->value);
      h = h->next;
   }
   printf("\n");
}