Circular Linked List Insertion and Deletion in C++

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#include<iostream>
using namespace std;

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

void insertStart (struct Node **head, int data)	//function to create linked list
{
  struct Node *newNode = (struct Node *) malloc (sizeof (struct Node));
  newNode->num = data;

  // if its the first node being entered
  if (*head == NULL)
    {
      *head = newNode;		// assigning itself as head
      (*head)->next = *head;	// assigning itself as next node

      cout << newNode->num << " Inserted\n"; return; } // if CLL already as >=1 node
  struct Node *curr = *head;

  // traverse till last node in CLL
  while (curr->next != *head)
    {
      curr = curr->next;
    }

  curr->next = newNode;		// last node's next as this new node
  newNode->next = *head;	// new node's next as current head node

  *head = newNode;		// changing head node to this new node
  cout << newNode->num << " Inserted\n"; // previous head node becomes 2nd node } void deleteBegin (struct Node **head) //function to delete beginning node from the circular linked list { struct Node *p, *temp; p = *head; while (p->next != (*head))
    {
      p = p->next;
    }
  temp = *head;
  p->next = (*head)->next;
  *head = (*head)->next;

  free (temp);
}

void deleteSpecific (struct Node **head, int pos)	//function to delete any node from the list
{
  if (pos < 1)
    {
      cout << "Invalid position entered"; } else if (pos == 1) { deleteBegin (head); } else { struct Node *p, *q; int del, k = 0; del = pos - 1; p = *head; while (k != del) { q = p; p = p->next;
	  k++;
	}
      q->next = p->next;
      free (p);			//deleting specific node
    }				//deleting specific node
}

void deleteEnd (struct Node **head)	//fuction to delete last node from the circular linked list
{
  struct Node *cur, *prev;
  cur = (*head);
  while (cur->next != *head)
    {
      prev = cur;
      cur = cur->next;
    }
  prev->next = *head;
  free (cur);
}

void display (struct Node *head)
{

  cout << "\nCircular Linked List : " << endl;

  // if circular linked list is empty currently
  if (head == NULL)
    return;

  struct Node *temp = head;

  // since we need to take care of circular nature of linked list
  do
    {
      cout << temp->num << " "; temp = temp->next;

    }
  while (temp != head);
  cout << endl;
}

int main ()				//main function
{
  // first node will be null at creation    
  struct Node *head = NULL;

  insertStart (&head, 1);
  insertStart (&head, 2);
  insertStart (&head, 3);
  insertStart (&head, 4);
  insertStart (&head, 5);

  display (head);
  deleteBegin(&head);

  cout<<"After deletion from beginning";
  display(head);

  deleteSpecific (&head, 3);
  cout << "After deletion from position 3";
  display (head);

  deleteEnd(&head);
  cout<<"After deletion from the end";
  display(head);

  return 0;
}

#include<iostream>
using namespace std;

class Node
{
public:
  int data;
  Node *next;
};

class LinkedList
{
private:
  Node * head;
public:
  LinkedList ()
  {				// constructor
    head = NULL;
  }
  int calcSize ();
  void deleteStart ();
  void deleteLast ();
  void deletePos (int pos);
  void display ();
  void insert (int data);
};

void LinkedList::deleteStart ()
{

  Node *temp = head;

  // if there are no nodes in Linked List can't delete
  if (head == NULL)
    {
      cout << "Circular Linked List Empty, deletion not possible\n";
      return;
    }

  // if only 1 node in CLL 
  if (temp->next == head)
    {
      head = NULL;
      return;
    }

  Node *curr = head;

  // traverse till last node in CLL
  while (curr->next != head)
    curr = curr->next;

  // assign last node's next to 2nd node in CLL
  curr->next = head->next;

  // move head to next node
  head = head->next;
  free (temp);
}

void LinkedList::deleteLast ()
{
  Node *temp = head;
  Node *previous;

  // if there are no nodes in Linked List can't delete
  if (head == NULL)
    {
      cout << "Circular Linked List Empty, deletion not possible\n";
      return;
    }
  // if Linked List has only 1 node 
  if (temp->next == head)
    {
      head = NULL;
      return;
    }

  // else traverse to the last node
  while (temp->next != head)
    {
      // store previous link node as we need to change its next val
      previous = temp;
      temp = temp->next;
    }
  // Curr assign 2nd last node's next to head
  previous->next = head;
  // delete the last node
  free (temp);
  // 2nd last now becomes the last node
}

void LinkedList::deletePos (int n)
{

  int size = calcSize ();

  if (n < 1 || size < n)
    {
      cout << "Insertion not possible" << n << " position invalid" << endl;
    }

  else if (n == 1)
    deleteStart ();

  else if (n == size)
    deleteLast ();

  else
    {
      Node *temp = head;
      Node *previous;

      // traverse to the nth node 
      while (--n)
	{
	  // store previous link node as we need to change its next val 
	  previous = temp;
	  temp = temp->next;
	}

      // change previous node's next node to nth node's next node
      previous->next = temp->next;
      // delete this nth node
      free (temp);
    }
}

void LinkedList::insert (int data)
{
  Node *newNode = new Node ();
  newNode->data = data;

  if (head == NULL)
    {
      head = newNode;
      head->next = head;
      return;
    }

  Node *curr = head;

  while (curr->next != head)
    {
      curr = curr->next;
    }

  curr->next = newNode;
  newNode->next = head;
  head = newNode;
}

int LinkedList::calcSize ()
{
  int size = 0;
  Node *temp = head;

  if (temp == NULL)
    return size;

  do
    {
      size++;
      temp = temp->next;

    }
  while (temp != head);

  return size;
}

void LinkedList::display ()
{
  // if circular linked list is empty currently
  if (head == NULL)
    return;

  Node *temp = head;

  // since we need to take care of circular nature of linked list
  do
    {
      cout << temp->data << " ";
      temp = temp->next;

    }
  while (temp != head);
  cout << endl;
}

int main ()
{
  // first node will be null at creation 
  LinkedList *list = new LinkedList ();

  list->insert (45);
  list->insert (36);
  list->insert (27);
  list->insert (18);
  list->insert (9);
  list->insert (0);

  list->display ();

  list->deleteStart ();
  list->display ();

  list->deleteLast ();
  list->display ();

  list->deletePos (3);
  list->display ();

  return 0;
}