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

struct list
{
  char data;
	struct list *prev;
  struct list *next;
};

typedef struct list LISTNODE;
typedef LISTNODE *LISTNODEPTR;

void insert (LISTNODEPTR *sPtr, char value)
{
  LISTNODEPTR newPtr, previousPtr, currentPtr;

  newPtr = malloc (sizeof (LISTNODE));

  if (newPtr != NULL)
  {
    newPtr->data = value;
    newPtr->next = NULL;
		newPtr->prev = NULL;

    previousPtr = NULL;
    currentPtr = *sPtr;

    while (currentPtr != NULL)
    {
      previousPtr = currentPtr;
      currentPtr = currentPtr->next;
    }

    if (previousPtr == NULL)
    {
      newPtr->next = *sPtr;
      *sPtr = newPtr;
    }
    else
    {
      previousPtr->next = newPtr;
			newPtr->prev = previousPtr;
      newPtr->next = currentPtr;
    }
  }
  else
    printf ("%c not inserted. No memory avilable.\n", value);
}

void printList (LISTNODEPTR currentPtr)
{
  if (currentPtr == NULL)
    printf("List is empty.\n\n");
  else
  {
    while (currentPtr != NULL)
    {
      printf("%c -> ", currentPtr->data);
      currentPtr = currentPtr->next;
    }
    printf ("NULL\n\n");
  }
}

LISTNODEPTR fillList (LISTNODEPTR nodePtr, int nodes_number)
{
  int i;
  char val;
  for (i = 0; i < 10; i++)
  {
    val = (rand () % 25) + 65;
    insert (&nodePtr, val);
  }
	return nodePtr;
}

void freeList (LISTNODEPTR list)
{
	if (list != NULL)
	{
		freeList (list->next);
		free (list);
	}
}

void reverse_list (LISTNODEPTR list)
{
	int list_length = 1, i;
	char tmp_data;
	LISTNODEPTR tmp_begin = list, tmp_end = list;
	while (tmp_end->next)
	{
		list_length++;
		tmp_end = tmp_end->next;
	}

	for (i = 0; i < list_length / 2; i++)
	{
		tmp_data = tmp_begin->data;
		tmp_begin->data = tmp_end->data;
		tmp_end->data = tmp_data;

		tmp_begin = tmp_begin->next;
		tmp_end = tmp_end->prev;
	}
}

int main (int argc, const char *argv[])
{
	LISTNODEPTR list = NULL;

	list = fillList (list, 10);
	printf ("Original list:\n");
	printList (list);
	reverse_list (list);
	printf ("Reversed list:\n");
	printList (list);
	freeList (list);

	return 0;
}