Deletion from end in circular linked list in C++

Deletion from end in circular linked list in C++

How to delete from end in circular linked list?

Deletion from end in circular linked list in C++ is one of the deletion operation that we can perform on the circular sequenced list. The other deletion operations that we can perform are:-

  • Deletion from beginning i.e. to delete the head node of the list.
  • Deletion from any specific position i.e. to delete any node from the list.

Steps to delete from end in circular linked list in CPP

  1. Print deletion not possible if list is empty.
  2. Else define two node pointers cur and prev
  3. Initialize cur pointer with head
  4. Change prev pointer to current and cur to cur->next until next of the current does not equal to head.
  5. Now link last second node that is the node pointed by prev node pointer to head.
  6. Free cur as it stores the last node of the list.
struct Node
{
  int num;
  struct Node *next;
};
Deletion in circular linked list in C++

Algorithm to write a CPP program to delete from end in Circular Linked List

  • STRUCT  CUR & PREV
  • CUR=HEAD
  • WHILE(CUR->NEXT!=HEAD)
  • PREV=CUR
  • CUR=CUR->NEXT
  • END WHILE
  • PREV->NEXT=HEAD
  • FREE(CUR)

C++ program for deletion from end in circular linked list

Run
#include<iostream>
using namespace std;

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

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 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);
  cout << "Before insertion ";
  display (head);
  deleteEnd (&head);
  cout << "After insertion ";
  display (head);
  return 0;
}
Output:
Enter the size of circular linked list: 6
Enter data of the list:
11
21
31
41
51
61

Circular linked list data:
11 21 31 41 51 61 
After deleting last node, new list is:
Circular linked list data:
11 21 31 41 51

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