Deletion at different positions in a Circular Linked List

Given a Circular Linked List. The task is to write programs to delete nodes from this list present at:

  • First position.
  • Last Position.
  • At any given position i.

Deleting first node from Singly Circular Linked List

Examples:

Input : 99->11->22->33->44->55->66
Output : 11->22->33->44->55->66

Input : 11->22->33->44->55->66
Output : 22->33->44->55->66
CircularDeleteFirstNode

Deleting First Node from Circular Linked List

Approach:

  1. Take two pointers current and previous and traverse the list.
  2. Keep the pointer current fixed pointing to the first node and move previous until it reaches the last node.
  3. Once, the pointer previous reaches the last node, do the following:
    • previous->next = current-> next
    • head = previous -> next;

Function to delete first node from singly circular linked list:

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// Function to delete First node of
// Circular Linked List
void DeleteFirst(struct Node** head)
{
    struct Node *previous = *head, *firstNode = *head;
  
    // check if list doesn't have any node
    // if not then return
    if (*head == NULL) {
        printf("\nList is empty\n");
        return;
    }
  
    // check if list have single node
    // if yes then delete it and return
    if (previous->next == previous) {
        *head = NULL;
        return;
    }
  
    // traverse second node to first
    while (previous->next != *head) {
  
        previous = previous->next;
    }
  
    // now previous is last node and
    // first node(firstNode) link address
    // put in last node(previous) link
    previous->next = firstNode->next;
  
    // make second node as head node
    *head = previous->next;
    free(firstNode);
    return;
}

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Deleting the last node of the Circular Linekd List

Examples:



Input : 99->11->22->33->44->55->66
Output : 99->11->22->33->44->55

Input : 99->11->22->33->44->55
Output : 99->11->22->33->44
CircularDeleteLastNode

Delete last node from Circular Linked List

Approach:

  1. Take two pointers current and previous and traverse the list.
  2. Move both pointers such that next of previous is always pointing to current. Keep moving the pointers current fand previous until current reaches the last node and previous is at second last node.
  3. Once, the pointer current reaches the last node, do the following:
    • previous->next = current-> next
    • head = previous -> next;

Function to delete last node from the list:

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// Function delete last node of
// Circular Linked List
void DeleteLast(struct Node** head)
{
    struct Node *current = *head, *temp = *head, *previous;
  
    // check if list doesn't have any node
    // if not then return
    if (*head == NULL) {
        printf("\nList is empty\n");
        return;
    }
  
    // check if list have single node
    // if yes then delete it and return
    if (current->next == current) {
        *head = NULL;
        return;
    }
  
    // move first node to last
    // previous
    while (current->next != *head) {
        previous = current;
        current = current->next;
    }
  
    previous->next = current->next;
    *head = previous->next;
    free(current);
    return;
}

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Deleting nodes at given index in the Circular linked list

Examples:

Input : 99->11->22->33->44->55->66
        Index= 4
Output : 99->11->22->33->55->66

Input : 99->11->22->33->44->55->66
        Index= 2
Output : 99->11->33->44->55->66

Note: 0-based indexing is considered for the list.

Approach:

  1. First, find the length of the list. That is, the number of nodes in the list.
  2. Take two pointers previous and current to traverse the list. Such that previous is one position behind the current node.
  3. Take a variable count initialized to 0 to keep track of the number of nodes traversed.
  4. Traverse the list until the given index is reached.
  5. Once the given index is reached, do previous->next = current->next.

Function to delete a node at given index or location from singly circular linked list:

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// Function to delete node at given index
// of Circular Linked List
void DeleteAtPosition(struct Node** head, int index)
{
    // find length of list
    int len = Length(*head);
    int count = 1;
    struct Node *previous = *head, *next = *head;
  
    // check if list doesn't have any node
    // if not then return
    if (*head == NULL) {
        printf("\nDelete Last List is empty\n");
        return;
    }
  
    // given index is in list or not
    if (index >= len || index < 0) {
        printf("\nIndex is not Found\n");
        return;
    }
  
    // delete first node
    if (index == 0) {
        DeleteFirst(head);
        return;
    }
  
    // traverse first to last node
    while (len > 0) {
  
        // if index found delete that node
        if (index == count) {
            previous->next = next->next;
            free(next);
            return;
        }
        previous = previous->next;
        next = previous->next;
        len--;
        count++;
    }
  
    return;
}

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Program implementing all of the above three functions

C++

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// C++ program to delete node at different
// poisitions from a circular linked list
#include <bits/stdc++.h>
using namespace std;
  
// structure for a node
struct Node {
    int data;
    struct Node* next;
};
  
// Function to insert a node at the end of
// a Circular linked list
void Insert(struct Node** head, int data)
{
    struct Node* current = *head;
    // Create a new node
    struct Node* newNode = new Node;
  
    // check node is created or not
    if (!newNode) {
        printf("\nMemory Error\n");
        return;
    }
  
    // insert data into newly created node
    newNode->data = data;
  
    // check list is empty
    // if not have any node then
    // make first node it
    if (*head == NULL) {
        newNode->next = newNode;
        *head = newNode;
        return;
    
  
    // if list have already some node
    else {
  
        // move first node to last node
        while (current->next != *head) {
            current = current->next;
        }
  
        // put first or head node address
        // in new node link
        newNode->next = *head;
  
        // put new node address into last
        // node link(next)
        current->next = newNode;
    }
}
  
// Function print data of list
void Display(struct Node* head)
{
    struct Node* current = head;
  
    // if list is empty, simply show message
    if (head == NULL) {
        printf("\nDisplay List is empty\n");
        return;
    }
  
    // traverse first to last node
    else {
        do {
            printf("%d ", current->data);
            current = current->next;
        } while (current != head);
    }
}
  
// Function return number of nodes present in list
int Length(struct Node* head)
{
    struct Node* current = head;
    int count = 0;
  
    // if list is empty simply return length zero
    if (head == NULL) {
        return 0;
    }
  
    // traverse forst to last node
    else {
        do {
            current = current->next;
            count++;
        } while (current != head);
    }
    return count;
}
  
// Function delete First node of Circular Linked List
void DeleteFirst(struct Node** head)
{
    struct Node *previous = *head, *next = *head;
  
    // check list have any node
    // if not then return
    if (*head == NULL) {
        printf("\nList is empty\n");
        return;
    }
  
    // check list have single node
    // if yes then delete it and return
    if (previous->next == previous) {
        *head = NULL;
        return;
    }
  
    // traverse second to first
    while (previous->next != *head) {
  
        previous = previous->next;
        next = previous->next;
    }
  
    // now previous is last node and
    // next is first node of list
    // first node(next) link address
    // put in last node(previous) link
    previous->next = next->next;
  
    // make second node as head node
    *head = previous->next;
    free(next);
  
    return;
}
  
// Function to delete last node of
// Circular Linked List
void DeleteLast(struct Node** head)
{
    struct Node *current = *head, *temp = *head, *previous;
  
    // check if list doesn't have any node
    // if not then return
    if (*head == NULL) {
        printf("\nList is empty\n");
        return;
    }
  
    // check if list have single node
    // if yes then delete it and return
    if (current->next == current) {
        *head = NULL;
        return;
    }
  
    // move first node to last
    // previous
    while (current->next != *head) {
        previous = current;
        current = current->next;
    }
  
    previous->next = current->next;
    *head = previous->next;
    free(current);
  
    return;
}
  
// Function delete node at a given poisition
// of Circular Linked List
void DeleteAtPosition(struct Node** head, int index)
{
    // Find length of list
    int len = Length(*head);
    int count = 1;
    struct Node *previous = *head, *next = *head;
  
    // check list have any node
    // if not then return
    if (*head == NULL) {
        printf("\nDelete Last List is empty\n");
        return;
    }
  
    // given index is in list or not
    if (index >= len || index < 0) {
        printf("\nIndex is not Found\n");
        return;
    }
  
    // delete first node
    if (index == 0) {
        DeleteFirst(head);
        return;
    }
  
    // traverse first to last node
    while (len > 0) {
  
        // if index found delete that node
        if (index == count) {
            previous->next = next->next;
            free(next);
            return;
        }
        previous = previous->next;
        next = previous->next;
        len--;
        count++;
    }
    return;
}
  
// Driver Code
int main()
{
    struct Node* head = NULL;
    Insert(&head, 99);
    Insert(&head, 11);
    Insert(&head, 22);
    Insert(&head, 33);
    Insert(&head, 44);
    Insert(&head, 55);
    Insert(&head, 66);
  
    // Deleting Node at position
    printf("Initial List: ");
    Display(head);
    printf("\nAfter Deleting node at index 4: ");
    DeleteAtPosition(&head, 4);
    Display(head);
  
    // Deleting first Node
    printf("\n\nInitial List: ");
    Display(head);
    printf("\nAfter Deleting first node: ");
    DeleteFirst(&head);
    Display(head);
  
    // Deleting last Node
    printf("\n\nInitial List: ");
    Display(head);
    printf("\nAfter Deleting last node: ");
    DeleteLast(&head);
    Display(head);
  
    return 0;
}

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Java

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// Java program to delete node at different
// poisitions from a circular linked list
import java.util.*;
import java.lang.*;
import java.io.*;
  
class GFG
{
  
// structure for a node
static class Node 
{
    int data;
    Node next;
};
  
// Function to insert a node at the end of
// a Circular linked list
static Node Insert(Node head, int data)
{
    Node current = head;
      
    // Create a new node
    Node newNode = new Node();
  
    // check node is created or not
    if (newNode == null)
    {
        System.out.printf("\nMemory Error\n");
        return null;
    }
  
    // insert data into newly created node
    newNode.data = data;
  
    // check list is empty
    // if not have any node then
    // make first node it
    if (head == null
    {
        newNode.next = newNode;
        head = newNode;
        return head;
    
  
    // if list have already some node
    else 
    {
  
        // move first node to last node
        while (current.next != head)
        {
            current = current.next;
        }
  
        // put first or head node address
        // in new node link
        newNode.next = head;
  
        // put new node address into last
        // node link(next)
        current.next = newNode;
    }
    return head;
}
  
// Function print data of list
static void Display( Node head)
{
    Node current = head;
  
    // if list is empty, simply show message
    if (head == null)
    {
        System.out.printf("\nDisplay List is empty\n");
        return;
    }
  
    // traverse first to last node
    else 
    {
        do 
        {
            System.out.printf("%d ", current.data);
            current = current.next;
        } while (current != head);
    }
}
  
// Function return number of nodes present in list
static int Length(Node head)
{
    Node current = head;
    int count = 0;
  
    // if list is empty 
    // simply return length zero
    if (head == null
    {
        return 0;
    }
  
    // traverse forst to last node
    else 
    {
        do
        {
            current = current.next;
            count++;
        } while (current != head);
    }
    return count;
}
  
// Function delete First node of
// Circular Linked List
static Node DeleteFirst(Node head)
{
    Node previous = head, next = head;
  
    // check list have any node
    // if not then return
    if (head == null
    {
        System.out.printf("\nList is empty\n");
        return null;
    }
  
    // check list have single node
    // if yes then delete it and return
    if (previous.next == previous) 
    {
        head = null;
        return null;
    }
  
    // traverse second to first
    while (previous.next != head)
    {
        previous = previous.next;
        next = previous.next;
    }
  
    // now previous is last node and
    // next is first node of list
    // first node(next) link address
    // put in last node(previous) link
    previous.next = next.next;
  
    // make second node as head node
    head = previous.next;
  
    return head;
}
  
// Function to delete last node of
// Circular Linked List
static Node DeleteLast(Node head)
{
    Node current = head, temp = head, previous=null;
  
    // check if list doesn't have any node
    // if not then return
    if (head == null)
    {
        System.out.printf("\nList is empty\n");
        return null;
    }
  
    // check if list have single node
    // if yes then delete it and return
    if (current.next == current) 
    {
        head = null;
        return null;
    }
  
    // move first node to last
    // previous
    while (current.next != head)
    {
        previous = current;
        current = current.next;
    }
  
    previous.next = current.next;
    head = previous.next;
      
    return head;
}
  
// Function delete node at a given poisition
// of Circular Linked List
static Node DeleteAtPosition( Node head, int index)
{
    // Find length of list
    int len = Length(head);
    int count = 1;
    Node previous = head, next = head;
  
    // check list have any node
    // if not then return
    if (head == null)
    {
        System.out.printf("\nDelete Last List is empty\n");
        return null;
    }
  
    // given index is in list or not
    if (index >= len || index < 0
    {
        System.out.printf("\nIndex is not Found\n");
        return null;
    }
  
    // delete first node
    if (index == 0
    {
        head = DeleteFirst(head);
        return head;
    }
  
    // traverse first to last node
    while (len > 0)
    {
  
        // if index found delete that node
        if (index == count)
        {
            previous.next = next.next;
              
            return head;
        }
        previous = previous.next;
        next = previous.next;
        len--;
        count++;
    }
    return head;
}
  
// Driver Code
public static void main(String args[])
{
    Node head = null;
    head = Insert(head, 99);
    head = Insert(head, 11);
    head = Insert(head, 22);
    head = Insert(head, 33);
    head = Insert(head, 44);
    head = Insert(head, 55);
    head = Insert(head, 66);
  
    // Deleting Node at position
    System.out.printf("Initial List: ");
    Display(head);
    System.out.printf("\nAfter Deleting node at index 4: ");
    head = DeleteAtPosition(head, 4);
    Display(head);
  
    // Deleting first Node
    System.out.printf("\n\nInitial List: ");
    Display(head);
    System.out.printf("\nAfter Deleting first node: ");
    head = DeleteFirst(head);
    Display(head);
  
    // Deleting last Node
    System.out.printf("\n\nInitial List: ");
    Display(head);
    System.out.printf("\nAfter Deleting last node: ");
    head = DeleteLast(head);
    Display(head);
}
}
  
// This code is contributed by Arnab Kundu

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Python

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# Python program to delete node at different
# positions from a circular linked list
  
# A linked list node
class Node: 
    def __init__(self, new_data): 
        self.data = new_data 
        self.next = None
        self.prev = None
  
# Function to insert a node at the end of
# a Circular linked list
def Insert(head, data):
  
    current = head
      
    # Create a new node
    newNode = Node(0)
  
    # check node is created or not
    if (newNode == None):
      
        print("\nMemory Error\n")
        return None
      
    # insert data into newly created node
    newNode.data = data
  
    # check list is empty
    # if not have any node then
    # make first node it
    if (head == None) :
        newNode.next = newNode
        head = newNode
        return head
  
    # if list have already some node
    else:
      
        # move first node to last node
        while (current.next != head):
          
            current = current.next
          
        # put first or head node address
        # in new node link
        newNode.next = head
  
        # put new node address into last
        # node link(next)
        current.next = newNode
      
    return head
  
# Function print data of list
def Display(head):
  
    current = head
  
    # if list is empty, simply show message
    if (head == None):
      
        print("\nDisplay List is empty\n")
        return
      
    # traverse first to last node
    else:
      
        while(True):
          
            print( current.data,end=" ")
            current = current.next
            if (current == head):
                break;
      
# Function return number of nodes present in list
def Length(head):
    current = head
    count = 0
  
    # if list is empty 
    # simply return length zero
    if (head == None): 
      
        return 0
  
    # traverse forst to last node
    else:
      
        while(True):
          
            current = current.next
            count = count + 1
            if (current == head):
                break;
      
    return count
  
# Function delete First node of
# Circular Linked List
def DeleteFirst(head):
    previous = head
    next = head
  
    # check list have any node
    # if not then return
    if (head == None) :
      
        print("\nList is empty")
        return None
      
    # check list have single node
    # if yes then delete it and return
    if (previous.next == previous) :
      
        head = None
        return None
      
    # traverse second to first
    while (previous.next != head):
        previous = previous.next
        next = previous.next
      
    # now previous is last node and
    # next is first node of list
    # first node(next) link address
    # put in last node(previous) link
    previous.next = next.next
  
    # make second node as head node
    head = previous.next
  
    return head
  
# Function to delete last node of
# Circular Linked List
def DeleteLast(head):
    current = head
    temp = head
    previous = None
  
    # check if list doesn't have any node
    # if not then return
    if (head == None):
        print("\nList is empty")
        return None
  
    # check if list have single node
    # if yes then delete it and return
    if (current.next == current) :
        head = None
        return None
  
    # move first node to last
    # previous
    while (current.next != head):
        previous = current
        current = current.next
      
    previous.next = current.next
    head = previous.next
      
    return head
  
# Function delete node at a given poisition
# of Circular Linked List
def DeleteAtPosition(head, index):
  
    # Find length of list
    len = Length(head)
    count = 1
    previous = head
    next = head
  
    # check list have any node
    # if not then return
    if (head == None):
        print("\nDelete Last List is empty")
        return None
      
    # given index is in list or not
    if (index >= len or index < 0) :
        print("\nIndex is not Found")
        return None
  
    # delete first node
    if (index == 0) :
        head = DeleteFirst(head)
        return head
  
    # traverse first to last node
    while (len > 0):
      
        # if index found delete that node
        if (index == count):
            previous.next = next.next
              
            return head
          
        previous = previous.next
        next = previous.next
        len = len - 1
        count = count + 1
      
    return head
  
# Driver Code
  
head = None
head = Insert(head, 99)
head = Insert(head, 11)
head = Insert(head, 22)
head = Insert(head, 33)
head = Insert(head, 44)
head = Insert(head, 55)
head = Insert(head, 66)
  
# Deleting Node at position
print("Initial List: ")
Display(head)
print("\nAfter Deleting node at index 4: ")
head = DeleteAtPosition(head, 4)
Display(head)
  
# Deleting first Node
print("\n\nInitial List: ")
Display(head)
print("\nAfter Deleting first node: ")
head = DeleteFirst(head)
Display(head)
  
# Deleting last Node
print("\n\nInitial List: ")
Display(head)
print("\nAfter Deleting last node: ")
head = DeleteLast(head)
Display(head)
  
# This code is contributed by Arnab Kundu

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C#

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// C# program to delete node at different 
// positions from a circular linked list 
using System;
  
class GFG 
  
// structure for a node 
class Node 
    public int data; 
    public Node next; 
}; 
  
// Function to insert a node at the end of 
// a Circular linked list 
static Node Insert(Node head, int data) 
    Node current = head; 
      
    // Create a new node 
    Node newNode = new Node(); 
  
    // check node is created or not 
    if (newNode == null
    
        Console.Write("\nMemory Error\n"); 
        return null
    
  
    // insert data into newly created node 
    newNode.data = data; 
  
    // check list is empty 
    // if not have any node then 
    // make first node it 
    if (head == null
    
        newNode.next = newNode; 
        head = newNode; 
        return head; 
    
  
    // if list have already some node 
    else
    
  
        // move first node to last node 
        while (current.next != head) 
        
            current = current.next; 
        
  
        // put first or head node address 
        // in new node link 
        newNode.next = head; 
  
        // put new node address into last 
        // node link(next) 
        current.next = newNode; 
    
    return head; 
  
// Function print data of list 
static void Display( Node head) 
    Node current = head; 
  
    // if list is empty, simply show message 
    if (head == null
    
        Console.Write("\nDisplay List is empty\n"); 
        return
    
  
    // traverse first to last node 
    else
    
        do
        
            Console.Write("{0} ", current.data); 
            current = current.next; 
        } while (current != head); 
    
  
// Function return number of nodes present in list 
static int Length(Node head) 
    Node current = head; 
    int count = 0; 
  
    // if list is empty 
    // simply return length zero 
    if (head == null
    
        return 0; 
    
  
    // traverse forst to last node 
    else
    
        do
        
            current = current.next; 
            count++; 
        } while (current != head); 
    
    return count; 
  
// Function delete First node of 
// Circular Linked List 
static Node DeleteFirst(Node head) 
    Node previous = head, next = head; 
  
    // check list have any node 
    // if not then return 
    if (head == null
    
        Console.Write("\nList is empty\n"); 
        return null
    
  
    // check list have single node 
    // if yes then delete it and return 
    if (previous.next == previous) 
    
        head = null
        return null
    
  
    // traverse second to first 
    while (previous.next != head) 
    
        previous = previous.next; 
        next = previous.next; 
    
  
    // now previous is last node and 
    // next is first node of list 
    // first node(next) link address 
    // put in last node(previous) link 
    previous.next = next.next; 
  
    // make second node as head node 
    head = previous.next; 
  
    return head; 
  
// Function to delete last node of 
// Circular Linked List 
static Node DeleteLast(Node head) 
    Node current = head, temp = head, previous = null
  
    // check if list doesn't have any node 
    // if not then return 
    if (head == null
    
        Console.Write("\nList is empty\n"); 
        return null
    
  
    // check if list have single node 
    // if yes then delete it and return 
    if (current.next == current) 
    
        head = null
        return null
    
  
    // move first node to last 
    // previous 
    while (current.next != head) 
    
        previous = current; 
        current = current.next; 
    
  
    previous.next = current.next; 
    head = previous.next; 
      
    return head; 
  
// Function delete node at a given poisition 
// of Circular Linked List 
static Node DeleteAtPosition( Node head, int index) 
    // Find length of list 
    int len = Length(head); 
    int count = 1; 
    Node previous = head, next = head; 
  
    // check list have any node 
    // if not then return 
    if (head == null
    
        Console.Write("\nDelete Last List is empty\n"); 
        return null
    
  
    // given index is in list or not 
    if (index >= len || index < 0) 
    
        Console.Write("\nIndex is not Found\n"); 
        return null
    
  
    // delete first node 
    if (index == 0) 
    
        head = DeleteFirst(head); 
        return head; 
    
  
    // traverse first to last node 
    while (len > 0) 
    
  
        // if index found delete that node 
        if (index == count) 
        
            previous.next = next.next; 
              
            return head; 
        
        previous = previous.next; 
        next = previous.next; 
        len--; 
        count++; 
    
    return head; 
  
// Driver Code 
public static void Main(String []args) 
    Node head = null
    head = Insert(head, 99); 
    head = Insert(head, 11); 
    head = Insert(head, 22); 
    head = Insert(head, 33); 
    head = Insert(head, 44); 
    head = Insert(head, 55); 
    head = Insert(head, 66); 
  
    // Deleting Node at position 
    Console.Write("Initial List: "); 
    Display(head); 
    Console.Write("\nAfter Deleting node at index 4: "); 
    head = DeleteAtPosition(head, 4); 
    Display(head); 
  
    // Deleting first Node 
    Console.Write("\n\nInitial List: "); 
    Display(head); 
    Console.Write("\nAfter Deleting first node: "); 
    head = DeleteFirst(head); 
    Display(head); 
  
    // Deleting last Node 
    Console.Write("\n\nInitial List: "); 
    Display(head); 
    Console.Write("\nAfter Deleting last node: "); 
    head = DeleteLast(head); 
    Display(head); 
  
// This code is contributed by Rajput-Ji

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Output:

Initial List: 99 11 22 33 44 55 66 
After Deleting node at index 4: 99 11 22 33 55 66 

Initial List: 99 11 22 33 55 66 
After Deleting first node: 11 22 33 55 66 

Initial List: 11 22 33 55 66 
After Deleting last node: 11 22 33 55

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Improved By : andrew1234, Rajput-Ji