Exchange first and last nodes in Circular Linked List

Given a Circular linked list exchange the first and the last node. The task should be done with only one extra node, you can not declare more than one extra node and also you are not allowed to declare any other temporary variable.
Note: Extra node means need of a node to traverse a list.
https://media.geeksforgeeks.org/wp-content/uploads/Capturehgh.png
Examples:

Input : 5 4 3 2 1
Output : 1 4 3 2 5

Input  : 6 1 2 3 4 5 6 7 8 9
Output : 9 1 2 3 4 5 6 7 8 6

We first find pointer to previous of last node. Let this node be p. Now we change next links so that the last and first nodes are swapped.

C++

filter_none

edit
close

play_arrow

link
brightness_4
code

// CPP program to exchange first and 
// last node in circular linked list
#include<bits/stdc++.h>
using namespace std;
  
struct Node
{
    int data;
    struct Node *next;
};
  
struct Node *addToEmpty(struct Node *head, int data)
{
    // This function is only for empty list
    if (head != NULL)
    return head;
  
    // Creating a node dynamically.
    struct Node *temp = 
        (struct Node*)malloc(sizeof(struct Node));
  
    // Assigning the data.
    temp -> data = data;
    head = temp;
  
    // Creating the link.
    head -> next = head;
  
    return head;
}
  
struct Node *addBegin(struct Node *head, int data)
{
    if (head == NULL)
        return addToEmpty(head, data);
  
    struct Node *temp =
        (struct Node *)malloc(sizeof(struct Node));
  
    temp -> data = data;
    temp -> next = head -> next;
    head -> next = temp;
  
    return head;
}
  
/* function for traversing the list */
void traverse(struct Node *head)
{
    struct Node *p;
  
    // If list is empty, return.
    if (head == NULL)
    {
        cout << "List is empty." << endl;
        return;
    }
  
    // Pointing to first Node of the list.
    p = head;
  
    // Traversing the list.
    do
    {
        cout << p -> data << " ";
        p = p -> next;
  
    } while(p != head);
}
  
/* Function to exchange first and last node*/
struct Node *exchangeNodes(struct Node *head)
{
    // Find pointer to previous of last node
    struct Node *p = head;
    while (p->next->next != head)
       p = p->next;
      
    /* Exchange first and last nodes using
       head and p */
    p->next->next = head->next;
    head->next = p->next;
    p->next = head;
    head = head->next;
  
    return head;
}
  
// Driven Program
int main()
{
    int i;
    struct Node *head = NULL;
    head = addToEmpty(head, 6);
      
    for (i = 5; i > 0; i--)
    head = addBegin(head, i);
    cout << "List Before: ";
    traverse(head);
    cout << endl;
      
    cout << "List After: ";
    head = exchangeNodes(head);
    traverse(head);
  
    return 0;
}

chevron_right






                        filter_none









Java














                                    filter_none




                                    edit

                                    close




                                    play_arrow




                                    link

                                    brightness_4

                                    code
                                




















// Java program to exchange  


// first and last node in  


// circular linked list 


class GFG 


{ 


  


static class Node 


{ 


    int data; 


    Node next; 


}; 


  


static Node addToEmpty(Node head,  


                       int data) 


{ 


    // This function is only 


    // for empty list 


    if (head != null) 


    return head; 


  


    // Creating a node dynamically. 


    Node temp = new Node(); 


  


    // Assigning the data. 


    temp.data = data; 


    head = temp; 


  


    // Creating the link. 


    head.next = head; 


  


    return head; 


} 


  


static Node addBegin(Node head, 


                     int data) 


{ 


    if (head == null) 


        return addToEmpty(head, data); 


  


    Node temp = new Node(); 


  


    temp.data = data; 


    temp.next = head.next; 


    head.next = temp; 


  


    return head; 


} 


  


// function for traversing the list  


static void traverse( Node head) 


{ 


    Node p; 


  


    // If list is empty, return. 


    if (head == null) 


    { 


        System.out.print("List is empty."); 


        return; 


    } 


  


    // Pointing to first  


    // Node of the list. 


    p = head; 


  


    // Traversing the list. 


    do


    { 


        System.out.print(p . data + " "); 


        p = p . next; 


  


    } while(p != head); 


} 


  


// Function to exchange  


// first and last node 


static Node exchangeNodes( Node head) 


{ 


    // Find pointer to previous 


    // of last node 


    Node p = head; 


    while (p.next.next != head) 


    p = p.next; 


      


    // Exchange first and last  


    // nodes using head and p 


    p.next.next = head.next; 


    head.next = p.next; 


    p.next = head; 


    head = head.next; 


  


    return head; 


} 


  


// Driver Code 


public static void main(String args[]) 


{ 


    int i; 


    Node head = null; 


    head = addToEmpty(head, 6); 


      


    for (i = 5; i > 0; i--) 


    head = addBegin(head, i); 


    System.out.print("List Before: "); 


    traverse(head); 


    System.out.println(); 


      


    System.out.print("List After: "); 


    head = exchangeNodes(head); 


    traverse(head); 


} 


} 


  


// This code is contributed  


// by Arnab Kundu 



















                        chevron_right







                        filter_none









Python3














                                    filter_none




                                    edit

                                    close




                                    play_arrow




                                    link

                                    brightness_4

                                    code
                                




















# Python3 program to exchange first and  


# last node in circular linked list 


import math 


  


class Node:  


    def __init__(self, data):  


        self.data = data  


        self.next = None


  


def addToEmpty(head, data): 


  


    # This function is only for empty list 


    if (head != None): 


        return head 


  


    # Creating a node dynamically. 


    temp = Node(data) 


  


    # Assigning the data. 


    temp.data = data 


    head = temp 


  


    # Creating the link. 


    head.next = head 


    return head 


  


def addBegin(head, data): 


  


    if (head == None): 


        return addToEmpty(head, data) 


  


    temp = Node(data) 


    temp.data = data 


    temp.next = head.next


    head.next = temp 


  


    return head 


  


# function for traversing the list  


def traverse(head): 


  


    # If list is empty, return. 


    if (head == None): 


      


        print("List is empty.") 


        return


      


    # Pointing to first Node of the list. 


    p = head 


    print(p.data, end = " ") 


    p = p.next


      


    # Traversing the list. 


    while(p != head): 


      


        print(p.data, end = " ") 


        p = p.next


  


def exchangeNodes(head): 


   


    # Find pointer to previous of last node 


    p = head 


    while (p.next.next != head): 


       p = p.next


        


    # Exchange first and last nodes 


    # using head and p  


    p.next.next = head.next


    head.next = p.next


    p.next = head 


    head = head.next


    


    return head 


   


# Driver Code 


if __name__=='__main__':  


  


    head = None


    head = addToEmpty(head, 6) 


    for x in range(5, 0, -1): 


        head = addBegin(head, x) 


    print("List Before: ", end = "") 


    traverse(head) 


    print() 


      


    print("List After: ", end = "") 


    head = exchangeNodes(head) 


    traverse(head) 


  


# This code is contributed by Srathore 



















                        chevron_right







                        filter_none









C#














                                    filter_none




                                    edit

                                    close




                                    play_arrow




                                    link

                                    brightness_4

                                    code
                                




















// C# program to exchange  


// first and last node in  


// circular linked list  


using System; 


  


public class GFG  


{  


  


    class Node  


    {  


        public int data;  


        public Node next;  


    };  


  


    static Node addToEmpty(Node head,  


                        int data)  


    {  


        // This function is only  


        // for empty list  


        if (head != null)  


        return head;  


  


        // Creating a node dynamically.  


        Node temp = new Node();  


  


        // Assigning the data.  


        temp.data = data;  


        head = temp;  


  


        // Creating the link.  


        head.next = head;  


  


        return head;  


    }  


  


    static Node addBegin(Node head,  


                        int data)  


    {  


        if (head == null)  


            return addToEmpty(head, data);  


  


        Node temp = new Node();  


  


        temp.data = data;  


        temp.next = head.next;  


        head.next = temp;  


  


        return head;  


    }  


  


    // function for traversing the list  


    static void traverse( Node head)  


    {  


        Node p;  


  


        // If list is empty, return.  


        if (head == null)  


        {  


            Console.Write("List is empty.");  


            return;  


        }  


  


        // Pointing to first  


        // Node of the list.  


        p = head;  


  


        // Traversing the list.  


        do


        {  


            Console.Write(p . data + " ");  


            p = p . next;  


  


        } while(p != head);  


    }  


  


    // Function to exchange  


    // first and last node  


    static Node exchangeNodes( Node head)  


    {  


        // Find pointer to previous  


        // of last node  


        Node p = head;  


        while (p.next.next != head)  


        p = p.next;  


  


        // Exchange first and last  


        // nodes using head and p  


        p.next.next = head.next;  


        head.next = p.next;  


        p.next = head;  


        head = head.next;  


  


        return head;  


    }  


  


    // Driver Code  


    public static void Main()  


    {  


        int i;  


        Node head = null;  


        head = addToEmpty(head, 6);  


  


        for (i = 5; i > 0; i--)  


        head = addBegin(head, i);  


        Console.Write("List Before: ");  


        traverse(head);  


        Console.WriteLine();  


  


        Console.Write("List After: ");  


        head = exchangeNodes(head);  


        traverse(head);  


    }  


}  


  


/* This code is contributed PrinciRaj1992 */



















                        chevron_right







                        filter_none










Output:


List Before: 6 1 2 3 4 5 
List After: 5 1 2 3 4 6 



This article is contributed by R_Raj. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@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.


Don’t stop now and take your learning to the next level. Learn all the important concepts of Data Structures and Algorithms with the help of the most trusted course: DSA Self Paced. Become industry ready at a student-friendly price.





    

        My Personal Notes
        arrow_drop_up
    

    

        
        

            
            
        

    


Recommended Posts: