Exchange first and last nodes in Circular Linked List
Last Updated :
22 Feb, 2023
Given 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 the 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
Method 1: (By Changing Links of First and Last Nodes)
We first find a pointer to the previous to the last node. Let this node be p. Now we change the 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;
}
// Java program to exchange
// first and last node in
// circular linked list
import java.util.*;
import java.io.*;
public 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
# 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)
// 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 */
<script>
// javascript program to exchange
// first and last node in
// circular linked list
class Node {
constructor() {
this.data = 0;
this.next = null;
}
}
function addToEmpty(head , data) {
// This function is only
// for empty list
if (head != null)
return head;
// Creating a node dynamically.
var temp = new Node();
// Assigning the data.
temp.data = data;
head = temp;
// Creating the link.
head.next = head;
return head;
}
function addBegin(head , data) {
if (head == null)
return addToEmpty(head, data);
var temp = new Node();
temp.data = data;
temp.next = head.next;
head.next = temp;
return head;
}
// function for traversing the list
function traverse(head) {
var p;
// If list is empty, return.
if (head == null) {
document.write("List is empty.");
return;
}
// Pointing to first
// Node of the list.
p = head;
// Traversing the list.
do {
document.write(p.data + " ");
p = p.next;
} while (p != head);
}
// Function to exchange
// first and last node
function exchangeNodes(head) {
// If list is of length 2
if (head.next.next == head) {
head = head.next;
return head;
}
// Find pointer to previous
// of last node
var 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
var i;
var head = null;
head = addToEmpty(head, 6);
for (i = 5; i > 0; i--)
head = addBegin(head, i);
document.write("List Before: ");
traverse(head);
document.write("<br/>");
document.write("List After: ");
head = exchangeNodes(head);
traverse(head);
// This code is contributed by umadevi9616
</script>
OutputList Before: 6 1 2 3 4 5
List After: 5 1 2 3 4 6
Time Complexity: O(n), as we are using a loop to traverse n times. Where n is the number of nodes in the linked list.
Auxiliary Space: O(1), as we are not using any extra space.
Method 2: (By Swapping Values of First and Last nodes)
Algorithm:
- Traverse the list and find the last node(tail).
- Swap data of head and tail.
Below is the implementation of the algorithm:
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 less than 2
if (head == NULL || head->next == NULL) {
return head;
}
Node* tail = head;
// Find pointer to the last node
while (tail->next != head) {
tail = tail->next;
}
/* Exchange first and last nodes using
head and p */
// temporary variable to store
// head data
int temp = tail->data;
tail->data = head->data;
head->data = temp;
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;
}
// JAVA program to exchange first and
// last node in circular linked list
import java.util.*;
import java.io.*;
public 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." +"\n");
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 less than 2
if (head == null || head.next == null) {
return head;
}
Node tail = head;
// Find pointer to the last node
while (tail.next != head) {
tail = tail.next;
}
/* Exchange first and last nodes using
head and p */
// temporary variable to store
// head data
int temp = tail.data;
tail.data = head.data;
head.data = temp;
return head;
}
// Driven Program
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 umadevi9616
# Python program to exchange first and
# last node in circular linked list class Node {
class Node:
def __init__(self):
self.data = 0
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()
# 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()
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
# Traversing the list.
while (True):
print(p.data, end=" ")
p = p.next
if(p == head):
break
# Function to exchange first and last node
def exchangeNodes(head):
# If list is of length less than 2
if (head == None or head.next == None):
return head
tail = head
# Find pointer to the last node
while (tail.next != head):
tail = tail.next
# Exchange first and last nodes using head and p
# temporary variable to store
# head data
temp = tail.data
tail.data = head.data
head.data = temp
return head
# Driven Program
head = None
head = addToEmpty(head, 6)
for i in range(5, 0, -1):
head = addBegin(head, i)
print("List Before: ")
traverse(head)
print("")
print("List After: ")
head = exchangeNodes(head)
traverse(head)
# This code is contributed by Saurabh Jaiswal
// C# program to exchange first and
// last node in circular linked list
using System;
public class GFG {
public 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." + "\n");
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 less than 2
if (head == null || head.next == null) {
return head;
}
Node tail = head;
// Find pointer to the last node
while (tail.next != head) {
tail = tail.next;
}
/*
* Exchange first and last nodes using head and p
*/
// temporary variable to store
// head data
int temp = tail.data;
tail.data = head.data;
head.data = temp;
return head;
}
// Driven Program
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);
Console.Write("List Before: ");
traverse(head);
Console.WriteLine();
Console.Write("List After: ");
head = exchangeNodes(head);
traverse(head);
}
}
// This code is contributed by umadevi9616
<script>
// javascript program to exchange first and
// last node in circular linked list class Node {
class Node {
constructor() {
this.data = 0;
this.next = null;
}
}
function addToEmpty(head , data) {
// This function is only for empty list
if (head != null)
return head;
// Creating a node dynamically.
var temp = new Node();
// Assigning the data.
temp.data = data;
head = temp;
// Creating the link.
head.next = head;
return head;
}
function addBegin(head , data) {
if (head == null)
return addToEmpty(head, data);
var temp = new Node();
temp.data = data;
temp.next = head.next;
head.next = temp;
return head;
}
/* function for traversing the list */
function traverse(head) {
var p;
// If list is empty, return.
if (head == null) {
document.write("List is empty." + "\n");
return;
}
// Pointing to first Node of the list.
p = head;
// Traversing the list.
do {
document.write(p.data + " ");
p = p.next;
} while (p != head);
}
/* Function to exchange first and last node */
function exchangeNodes(head) {
// If list is of length less than 2
if (head == null || head.next == null) {
return head;
}
var tail = head;
// Find pointer to the last node
while (tail.next != head) {
tail = tail.next;
}
/*
* Exchange first and last nodes using head and p
*/
// temporary variable to store
// head data
var temp = tail.data;
tail.data = head.data;
head.data = temp;
return head;
}
// Driven Program
var i;
var head = null;
head = addToEmpty(head, 6);
for (i = 5; i > 0; i--)
head = addBegin(head, i);
document.write("List Before: <br/>");
traverse(head);
document.write("<br/>");
document.write("List After: <br/>");
head = exchangeNodes(head);
traverse(head);
// This code is contributed by umadevi9616
</script>
OutputList Before: 6 1 2 3 4 5
List After: 5 1 2 3 4 6
Time Complexity: O(n), as we are using a loop to traverse n times. Where n is the number of nodes in the linked list.
Auxiliary Space: O(1), as we are not using any extra space.
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Pattern SearchingPattern searching algorithms are essential tools in computer science and data processing. These algorithms are designed to efficiently find a particular pattern within a larger set of data. Patten SearchingImportant Pattern Searching Algorithms:Naive String Matching : A Simple Algorithm that works i
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GeometryGeometry is a branch of mathematics that studies the properties, measurements, and relationships of points, lines, angles, surfaces, and solids. From basic lines and angles to complex structures, it helps us understand the world around us.Geometry for Students and BeginnersThis section covers key br
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