Deletion from a Circular Linked List - GeeksforGeeks

23 Nov, 2021
We have already discussed circular linked list and traversal in a circular linked list in the below articles: Introduction to circular linked list Traversal in a circular linked list In this article, we will learn about deleting a node from a circular linked list. Consider the linked list as shown below:  
We will be given a node and our task is to delete that node from the circular linked list.
Examples: 
Input : 2->5->7->8->10->(head node)
        data = 5
Output : 2->7->8->10->(head node)

Input : 2->5->7->8->10->(head node)
         7
Output : 2->5->8->10->(head node)
AlgorithmCase 1: List is empty. 
If the list is empty we will simply return.
Case 2:List is not empty  
If the list is not empty then we define two pointers curr and prev and initialize the pointer curr with the head node.
Traverse the list using curr to find the node to be deleted and before moving to curr to the next node, every time set prev = curr.
If the node is found, check if it is the only node in the list. If yes, set head = NULL and free(curr).
If the list has more than one node, check if it is the first node of the list. Condition to check this( curr == head). If yes, then move prev until it reaches the last node. After prev reaches the last node, set head = head -> next and prev -> next = head. Delete curr.
If curr is not the first node, we check if it is the last node in the list. Condition to check this is (curr -> next == head).
If curr is the last node. Set prev -> next = head and delete the node curr by free(curr).
If the node to be deleted is neither the first node nor the last node, then set prev -> next = curr -> next and delete curr.
Complete program to demonstrate deletion in Circular Linked List: 
C++14
C
Java
Python
C#
Javascript
// C++ program to delete a given key from// linked list.#include <bits/stdc++.h>using namespace std; /* structure for a node */class Node {public:    int data;    Node* next;}; /* Function to insert a node at the beginning ofa Circular linked list */void push(Node** head_ref, int data){    // Create a new node and make head as next    // of it.    Node* ptr1 = new 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.        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 givencircular linked list */void printList(Node* head){    Node* temp = head;    if (head != NULL) {        do {            cout << temp->data << " ";            temp = temp->next;        } while (temp != head);    }     cout << endl;} /* Function to delete a given node from the list */void deleteNode(Node** head, int key){         // If linked list is empty    if (*head == NULL)        return;             // If the list contains only a single node    if((*head)->data==key && (*head)->next==*head)    {        free(*head);        *head=NULL;        return;    }         Node *last=*head,*d;         // If head is to be deleted    if((*head)->data==key)    {                 // Find the last node of the list        while(last->next!=*head)            last=last->next;                     // Point last node to the next of head i.e.        // the second node of the list        last->next=(*head)->next;        free(*head);        *head=last->next;      return;    }         // Either the node to be deleted is not found    // or the end of list is not reached    while(last->next!=*head&&last->next->data!=key)    {        last=last->next;    }         // If node to be deleted was found    if(last->next->data==key)    {        d=last->next;        last->next=d->next;        free(d);    }    else        cout<<"no such keyfound";    } /* Driver code */int main(){    /* Initialize lists as empty */    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);     cout << "List Before Deletion: ";    printList(head);     deleteNode(&head, 7);     cout << "List After Deletion: ";    printList(head);     return 0;} // This is code is contributed by rathbhupendra
// 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;}
// Java program to delete a given key from// linked list.class GFG {     /* ure for a node */    static class Node {        int data;        Node next;    };     /* Function to insert a node at the beginning ofa Circular linked list */    static Node push(Node head_ref, int data)    {        // Create a new node and make head as next        // of it.        Node ptr1 = new 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.            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;        return head_ref;    }     /* Function to print nodes in a givencircular linked list */    static void printList(Node head)    {        Node temp = head;        if (head != null) {            do {                System.out.printf("%d ", temp.data);                temp = temp.next;            } while (temp != head);        }         System.out.printf("\n");    }     /* Function to delete a given node from the list */    static Node deleteNode(Node head, int key)    {        if (head == null)            return null;         // Find the required node        Node curr = head, prev = new Node();        while (curr.data != key) {            if (curr.next == head) {                System.out.printf("\nGiven node is not found"                                  + " in the list!!!");                break;            }             prev = curr;            curr = curr.next;        }         // Check if node is only node        if (curr == head && curr.next == head) {            head = null;            return head;        }         // 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;        }         // check if node is last node        else if (curr.next == head) {            prev.next = head;        }        else {            prev.next = curr.next;        }        return head;    }     /* Driver code */    public static void main(String args[])    {        /* Initialize lists as empty */        Node head = null;         /* Created linked list will be 2.5.7.8.10 */        head = push(head, 2);        head = push(head, 5);        head = push(head, 7);        head = push(head, 8);        head = push(head, 10);         System.out.printf("List Before Deletion: ");        printList(head);         head = deleteNode(head, 7);         System.out.printf("List After Deletion: ");        printList(head);    }} // This code is contributed by Arnab Kundu
# Python program to delete a given key from# linked list. # Node of a doubly linked listclass Node:    def __init__(self, next = None, data = None):        self.next = next        self.data = data # Function to insert a node at the beginning of# a Circular linked listdef push(head_ref, data):     # Create a new node and make head as next    # of it.    ptr1 = Node()    ptr1.data = data    ptr1.next = head_ref     # If linked list is not None then set the    # next of last node    if (head_ref != None) :                 # Find the node before head and update        # next of it.        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    return head_ref # Function to print nodes in a given# circular linked listdef printList( head):     temp = head    if (head != None) :        while(True) :            print( temp.data, end = " ")            temp = temp.next            if (temp == head):                break    print() # Function to delete a given node from the listdef deleteNode( head, key) :     # If linked list is empty    if (head == None):        return             # If the list contains only a single node    if((head).data == key and (head).next == head):             head = None         last = head    d = None         # If head is to be deleted    if((head).data == key) :                 # Find the last node of the list        while(last.next != head):            last = last.next                     # Point last node to the next of head i.e.        # the second node of the list        last.next = (head).next        head = last.next         # Either the node to be deleted is not found    # or the end of list is not reached    while(last.next != head and last.next.data != key) :        last = last.next     # If node to be deleted was found    if(last.next.data == key) :        d = last.next        last.next = d.next         else:        print("no such keyfound")         return head # Driver code # Initialize lists as emptyhead = None # Created linked list will be 2.5.7.8.10head = push(head, 2)head = push(head, 5)head = push(head, 7)head = push(head, 8)head = push(head, 10) print("List Before Deletion: ")printList(head) head = deleteNode(head, 7) print( "List After Deletion: ")printList(head) # This code is contributed by Arnab Kundu
// C# program to delete a given key from// linked list.using System; class GFG {     /* structure for a node */    public class Node {        public int data;        public Node next;    };     /* Function to insert a node at the beginning ofa Circular linked list */    static Node push(Node head_ref, int data)    {        // Create a new node and make head as next        // of it.        Node ptr1 = new 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.            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;        return head_ref;    }     /* Function to print nodes in a given       circular linked list */    static void printList(Node head)    {        Node temp = head;        if (head != null)        {            do            {                Console.Write("{0} ", temp.data);                temp = temp.next;            } while (temp != head);        }         Console.Write("\n");    }     /* Function to delete a given node from the list */    static Node deleteNode(Node head, int key)    {        if (head == null)            return null;         // Find the required node        Node curr = head, prev = new Node();        while (curr.data != key)        {            if (curr.next == head)            {                Console.Write("\nGiven node is not found"                              + " in the list!!!");                break;            }             prev = curr;            curr = curr.next;        }         // Check if node is only node        if (curr.next == head && curr == head)        {            head = null;            return head;        }         // 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;        }         // check if node is last node        else if (curr.next == head)        {            prev.next = head;        }        else        {            prev.next = curr.next;        }        return head;    }     /* Driver code */    public static void Main(String[] args)    {        /* Initialize lists as empty */        Node head = null;         /* Created linked list will be 2.5.7.8.10 */        head = push(head, 2);        head = push(head, 5);        head = push(head, 7);        head = push(head, 8);        head = push(head, 10);         Console.Write("List Before Deletion: ");        printList(head);         head = deleteNode(head, 7);         Console.Write("List After Deletion: ");        printList(head);    }} // This code has been contributed by 29AjayKumar
<script>// javascript program to delete a given key from// linked list.    /* ure for a node */class Node {    constructor() {        this.data = 0;        this.next = null;    }}    /*     * Function to insert a node at the beginning of a Circular linked list     */    function push(head_ref , data) {        // Create a new node and make head as next        // of it.        var ptr1 = new 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.            var 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;        return head_ref;    }     /*     * Function to print nodes in a given circular linked list     */    function printList(head) {    var temp = head;        if (head != null) {            do {                document.write( temp.data+" ");                temp = temp.next;            } while (temp != head);        }         document.write("<br/>");    }     /* Function to delete a given node from the list */    function deleteNode(head , key) {        if (head == null)            return null;         // Find the required node        var curr = head, prev = new Node();        while (curr.data != key) {            if (curr.next == head) {                document.write("<br/>Given node is not found" + " in the list!!!");                break;            }             prev = curr;            curr = curr.next;        }         // Check if node is only node        if (curr == head && curr.next == head) {            head = null;            return head;        }         // 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;        }         // check if node is last node        else if (curr.next == head) {            prev.next = head;        } else {            prev.next = curr.next;        }        return head;    }         /* Driver code */             /* Initialize lists as empty */        var head = null;         /* Created linked list will be 2.5.7.8.10 */        head = push(head, 2);        head = push(head, 5);        head = push(head, 7);        head = push(head, 8);        head = push(head, 10);         document.write("List Before Deletion: ");        printList(head);         head = deleteNode(head, 7);         document.write("List After Deletion: ");        printList(head); // This code contributed by umadevi9616</script>
List Before Deletion: 10 8 7 5 2 
List After Deletion: 10 8 5 2 

This article is contributed by Harsh Agarwal. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
andrew1234
rathbhupendra
29AjayKumar
rudrathechamp007
yanshika00
vvkbisht
sky8214
umadevi9616
paritoshdev26
ankita_saini
gs0801it191075
circular linked list
Linked List
Linked List
circular linked list
Writing code in comment?
Please use ide.geeksforgeeks.org,
generate link and share the link here.
Comments
Old Comments
Linked List | Set 1 (Introduction)
Linked List | Set 2 (Inserting a node)
Stack Data Structure (Introduction and Program)
Linked List | Set 3 (Deleting a node)
LinkedList in Java
Linked List vs Array
Delete a Linked List node at a given position
Implementing a Linked List in Java using Class
Detect loop in a linked list
Merge two sorted linked lists