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

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

typedef struct Node Node;

/*************************************/
/* FUNCTION TO REVERSE A LINKED LIST */
Node* reverse(Node* iter)
{
  Node* prev = 0;
  Node* next = 0;
  while(iter)
  {
    next = iter->next;
    iter->next = prev;
    prev = iter;
    iter = next;
  }
  return prev;
}
/*************************************/

void print_list(Node* iter)
{
  fprintf(stdout, ": ");

  while (iter)
  {
    fprintf(stdout, "%d ", iter->data);
    iter = iter->next;
  }
  fprintf(stdout, "\n");
}

int main(int argc, char** argv)
{
  int i;
  Node *head, *iter;

  head = malloc(sizeof(Node));
  head->data = 1;
  iter = head;

  for (i = 2; i <=20; ++i)
  {
    iter->next = malloc(sizeof(Node));
    iter->next->data = i;
    iter = iter->next;
  }
  iter->next = 0;
  
  print_list(head);
  head = reverse(head);
  print_list(head);
  head = reverse(head);
  print_list(head);

  iter = head;
  while (iter)
  {
    head = iter;
    iter = iter->next;
    free(head);
  }
  
  return 0;
}