Anticlockwise spiral conversion of doubly linked list in c

C program for Anticlockwise spiral conversion of doubly linked list. Here problem description and explanation.

// Include header file
#include <stdio.h>
#include <stdlib.h>

// C program for
// Convert a doubly linked list anticlockwise spiral form

// This is Linked List Node
typedef struct LinkNode
{
	// Define useful field of LinkNode
	int data;
	struct LinkNode * next;
	struct LinkNode * prev;
}LinkNode;

LinkNode * getLinkNode(int data)
{
	// Create dynamic memory of LinkNode
	LinkNode * ref = (LinkNode * ) malloc(sizeof(LinkNode));
	if (ref == NULL)
	{
		// Failed to create memory 
		return NULL;
	}
	ref->data = data;
	ref->next = NULL;
	ref->prev = NULL;
	return ref;
}

typedef struct DoublyLinkedList
{
	// Define useful field of DoublyLinkedList
	struct LinkNode * head;
	struct LinkNode * tail;
}DoublyLinkedList;

DoublyLinkedList * getDoublyLinkedList()
{
	// Create dynamic memory of DoublyLinkedList
	DoublyLinkedList * ref = 
      (DoublyLinkedList * ) malloc(sizeof(DoublyLinkedList));
	if (ref == NULL)
	{
		// Failed to create memory 
		return NULL;
	}
	// Set head and tail
	ref->head = NULL;
	ref->tail = NULL;
	return ref;
}
// Insert new node at end position
void insert(DoublyLinkedList * ref, int value)
{
	// Create a node
	LinkNode * node = getLinkNode(value);
	if (ref->head == NULL)
	{
		// Add first node
		ref->head = node;
		ref->tail = node;
		return;
	}
	// Add node at last position
	ref->tail->next = node;
	node->prev = ref->tail;
	ref->tail = node;
}
// Display node element of doubly linked list
void display(DoublyLinkedList * ref)
{
	if (ref->head == NULL)
	{
		printf("Empty Linked List");
	}
	else
	{
		printf("\nLinked List Head to Tail :");
		// Get first node of linked list
		LinkNode * temp = ref->head;
		// iterate linked list 
		while (temp != NULL)
		{
			// Display node value
			printf(" %d ", temp->data);
			// Visit to next node
			temp = temp->next;
		}
		printf("\nLinked List Tail to Head :");
		// Get last node of linked list
		temp = ref->tail;
		// iterate linked list 
		while (temp != NULL)
		{
			// Display node value
			printf(" %d ", temp->data);
			// Visit to prev node
			temp = temp->prev;
		}
	}
}
void spiralTransform(DoublyLinkedList * ref)
{
	if (ref->head == NULL || ref->head->next == NULL)
	{
		return;
	}
	LinkNode * last = ref->tail;
	LinkNode * current = ref->head;
	LinkNode * auxiliary = NULL;
	LinkNode * temp = NULL;
	LinkNode * back = NULL;
	// Set new head
	ref->head = ref->tail;
	while (current != NULL && last != NULL)
	{
		if (current == last)
		{
			current->next = NULL;
			current->prev = back;
			ref->tail = current;
			// Set new last node
			return;
		}
		else if (current->next == last)
		{
			current->next = NULL;
			current->prev = last;
			last->next = current;
			last->prev = back;
			// Set new last node
			ref->tail = current;
			return;
		}
		// Swap link
		auxiliary = current->next;
		temp = last->prev;
		current->prev = last;
		last->next = current;
		current->next = temp;
		last->prev = back;
		back = current;
		current = auxiliary;
		last = temp;
	}
}
int main()
{
	DoublyLinkedList * dll = getDoublyLinkedList();
	// Insert following linked list nodes
	insert(dll, 1);
	insert(dll, 2);
	insert(dll, 3);
	insert(dll, 4);
	insert(dll, 5);
	insert(dll, 6);
	insert(dll, 7);
	insert(dll, 8);
	insert(dll, 9);
	printf("\nBefore anticlockwise spiral conversion");
	// Display all node
	display(dll);
	printf("\nAfter anticlockwise spiral conversion");
	spiralTransform(dll);
	display(dll);
}

Output

Before anticlockwise spiral conversion
Linked List Head to Tail : 1  2  3  4  5  6  7  8  9
Linked List Tail to Head : 9  8  7  6  5  4  3  2  1
After anticlockwise spiral conversion
Linked List Head to Tail : 9  1  8  2  7  3  6  4  5
Linked List Tail to Head : 5  4  6  3  7  2  8  1  9