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.
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++
// 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) { // If list is of length 2 if (head->next->next == head) { head = head->next; return 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
// 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) { // If list is of length 2 if (head.next.next == head) { head = head.next; return 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
# 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): # Cases Handled: Linked List either empty or containing single node. if head == None or head.next == head: return head # Cases Handled: Linked List containing only two nodes elif head.next.next == head: head = head.next return head # Cases Handled: Linked List containing multiple nodes else: prev = None curr = head temp = head # finding last and second last nodes in linkedlist list while curr.next != head: prev = curr curr = curr.next # point the last node to second node of the list curr.next = temp.next # point the second last node to first node prev.next = temp # point the end of node to start ( make linked list circular ) temp.next = curr # mark the starting of linked list head = curr 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 # Improved by Vinay Kumar (vinaykumar71) |
chevron_right
filter_none
C#
// 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) { // If list is of length 2 if (head.next.next == head) { head = head.next; return 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.
Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.
