Circular delete.txt

Step 1: IF HEAD = NULL
  Write UNDERFLOW
   Go to Step 8
  [END OF IF]

Step 2: SET PTR = HEAD
Step 3: Repeat Steps 4 and 5 while PTR -> NEXT != HEAD
Step 4: SET PREPTR = PTR
Step 5: SET PTR = PTR -> NEXT
[END OF LOOP]

Step 6: SET PREPTR -> NEXT = HEAD
Step 7: FREE PTR
Step 8: EXIT******************************


// C program to delete a given key from
// linked list.
#include <stdio.h>
#include <stdlib.h>

/* structure for a node */
struct Node {
	int data;
	struct Node* next;
};

/* Function to insert a node at the beginning of
a Circular linked list */
void push(struct Node** head_ref, int data)
{
	// Create a new node and make head as next
	// of it.
	struct Node* ptr1 = (struct Node*)malloc(sizeof(struct Node));
	ptr1->data = data;
	ptr1->next = *head_ref;

	/* If linked list is not NULL then set the
	next of last node */
	if (*head_ref != NULL) {
		// Find the node before head and update
		// next of it.
		struct Node* temp = *head_ref;
		while (temp->next != *head_ref)
			temp = temp->next;
		temp->next = ptr1;
	}
	else
		ptr1->next = ptr1; /*For the first node */

	*head_ref = ptr1;
}

/* Function to print nodes in a given
circular linked list */
void printList(struct Node* head)
{
	struct Node* temp = head;
	if (head != NULL) {
		do {
			printf("%d ", temp->data);
			temp = temp->next;
		} while (temp != head);
	}

	printf("\n");
}

/* Function to delete a given node from the list */
void deleteNode(struct Node* head, int key)
{
	if (head == NULL)
		return;

	// Find the required node
	struct Node *curr = head, *prev;
	while (curr->data != key)
	{
		if (curr->next == head)
		{
			printf("\nGiven node is not found"
				" in the list!!!");
			break;
		}

		prev = curr;
		curr = curr->next;
	}

	// Check if node is only node
	if (curr->next == head)
	{
		head = NULL;
		free(curr);
		return;
	}

	// If more than one node, check if
	// it is first node
	if (curr == head)
	{
		prev = head;
		while (prev->next != head)
			prev = prev->next;
		head = curr->next;
		prev->next = head;
		free(curr);
	}

	// check if node is last node
	else if (curr->next == head && curr == head)
	{
		prev->next = head;
		free(curr);
	}
	else
	{
		prev->next = curr->next;
		free(curr);
	}
}

/* Driver code */
int main()
{
	/* Initialize lists as empty */
	struct Node* head = NULL;

	/* Created linked list will be 2->5->7->8->10 */
	push(&head, 2);
	push(&head, 5);
	push(&head, 7);
	push(&head, 8);
	push(&head, 10);

	printf("List Before Deletion: ");
	printList(head);

	deleteNode(head, 7);

	printf("List After Deletion: ");
	printList(head);

	return 0;
}