Reverse a circular linked list
Given a circular linked list of size n. The problem is to reverse the given circular linked list by changing links between the nodes.
Examples:
INPUT:
OUTPUT:
Approach: The approach is same as followed in reversing a singly linked list. Only here we have to make one more adjustment by linking the last node of the reversed list to the first node.
C++
// C++ implementation to reverse // a circular linked list #include <bits/stdc++.h> using namespace std; // Linked list node struct Node { int data; Node* next; }; // function to get a new node Node* getNode(int data) { // allocate memory for node Node* newNode = new Node; // put in the data newNode->data = data; newNode->next = NULL; return newNode; } // Function to reverse the circular linked list void reverse(Node** head_ref) { // if list is empty if (*head_ref == NULL) return; // reverse procedure same as reversing a // singly linked list Node* prev = NULL; Node* current = *head_ref; Node* next; do { next = current->next; current->next = prev; prev = current; current = next; } while (current != (*head_ref)); // adjutsing the links so as to make the // last node point to the first node (*head_ref)->next = prev; *head_ref = prev; } // Function to print circular linked list void printList(Node* head) { if (head == NULL) return; Node* temp = head; do { cout << temp->data << " "; temp = temp->next; } while (temp != head); } // Driver program to test above int main() { // Create a circular linked list // 1->2->3->4->1 Node* head = getNode(1); head->next = getNode(2); head->next->next = getNode(3); head->next->next->next = getNode(4); head->next->next->next->next = head; cout << "Given circular linked list: "; printList(head); reverse(&head); cout << "\nReversed circular linked list: "; printList(head); return 0; } |
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Java
// Java implementation to reverse // a circular linked list class GFG { // Linked list node static class Node { int data; Node next; }; // function to get a new node static Node getNode(int data) { // allocate memory for node Node newNode = new Node(); // put in the data newNode.data = data; newNode.next = null; return newNode; } // Function to reverse the circular linked list static Node reverse(Node head_ref) { // if list is empty if (head_ref == null) return null; // reverse procedure same as reversing a // singly linked list Node prev = null; Node current = head_ref; Node next; do { next = current.next; current.next = prev; prev = current; current = next; } while (current != (head_ref)); // adjutsing the links so as to make the // last node point to the first node (head_ref).next = prev; head_ref = prev; return head_ref; } // Function to print circular linked list static void printList(Node head) { if (head == null) return; Node temp = head; do { System.out.print( temp.data + " "); temp = temp.next; } while (temp != head); } // Driver code public static void main(String args[]) { // Create a circular linked list // 1.2.3.4.1 Node head = getNode(1); head.next = getNode(2); head.next.next = getNode(3); head.next.next.next = getNode(4); head.next.next.next.next = head; System.out.print("Given circular linked list: "); printList(head); head = reverse(head); System.out.print("\nReversed circular linked list: "); printList(head); } } // This code is contributed by Arnab Kundu |
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Python3
# Python3 implementation to reverse # a circular linked list import math # Linked list node class Node: def __init__(self, data): self.data = data self.next = None # function to get a new node def getNode(data): # allocate memory for node newNode = Node(data) # put in the data newNode.data = data newNode.next = None return newNode # Function to reverse the # circular linked list def reverse(head_ref): # if list is empty if (head_ref == None): return None # reverse procedure same as # reversing a singly linked list prev = None current = head_ref next = current.next current.next = prev prev = current current = next while (current != head_ref): next = current.next current.next = prev prev = current current = next # adjutsing the links so as to make the # last node po to the first node head_ref.next = prev head_ref = prev return head_ref # Function to print circular linked list def prList(head): if (head == None): return temp = head print(temp.data, end = " ") temp = temp.next while (temp != head): print(temp.data, end = " ") temp = temp.next # Driver Code if __name__=='__main__': # Create a circular linked list # 1.2.3.4.1 head = getNode(1) head.next = getNode(2) head.next.next = getNode(3) head.next.next.next = getNode(4) head.next.next.next.next = head print("Given circular linked list: ", end = "") prList(head) head = reverse(head) print("\nReversed circular linked list: ", end = "") prList(head) # This code is contributed by Srathore |
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C#
// C# implementation to reverse // a circular linked list using System; class GFG { // Linked list node public class Node { public int data; public Node next; }; // function to get a new node static Node getNode(int data) { // allocate memory for node Node newNode = new Node(); // put in the data newNode.data = data; newNode.next = null; return newNode; } // Function to reverse the circular linked list static Node reverse(Node head_ref) { // if list is empty if (head_ref == null) return null; // reverse procedure same as reversing a // singly linked list Node prev = null; Node current = head_ref; Node next; do { next = current.next; current.next = prev; prev = current; current = next; } while (current != (head_ref)); // adjutsing the links so as to make the // last node point to the first node (head_ref).next = prev; head_ref = prev; return head_ref; } // Function to print circular linked list static void printList(Node head) { if (head == null) return; Node temp = head; do { Console.Write( temp.data + " "); temp = temp.next; } while (temp != head); } // Driver code public static void Main(String []args) { // Create a circular linked list // 1.2.3.4.1 Node head = getNode(1); head.next = getNode(2); head.next.next = getNode(3); head.next.next.next = getNode(4); head.next.next.next.next = head; Console.Write("Given circular linked list: "); printList(head); head = reverse(head); Console.Write("\nReversed circular linked list: "); printList(head); } } // This code contributed by Rajput-Ji |
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Output:
Given circular linked list: 1 2 3 4 Reversed circular linked list: 4 3 2 1
Time Complexity: O(n)
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