Move first element to end of a given Linked List
Write a C function that moves first element to end in a given Singly Linked List. For example, if the given Linked List is 1->2->3->4->5, then the function should change the list to 2->3->4->5->1.
Algorithm:
Traverse the list till last node. Use two pointers: one to store the address of last node(last) and other for address of first node(first). After the end of loop do following operations.
- Make head as second node (*head_ref = first->next).
- Set next of first as NULL (first->next = NULL).
- Set next of last as first ( last->next = first)
Steps to solve the problem:
1. check if *head_ref is equal to null or *head_ref ->next is null than return.
2. declare two node pointers first and second.
3. while last->next is not null:
* update last to last->next.
4. update *head_ref to first->next.
5. point first->next to null.
6. point last->next to first.
Implementation:
C++
#include <stdio.h>
#include <stdlib.h>
struct Node {
int data;
struct Node* next;
};
void moveToEnd( struct Node** head_ref)
{
if (*head_ref == NULL || (*head_ref)->next == NULL)
return ;
struct Node* first = *head_ref;
struct Node* last = *head_ref;
while (last->next != NULL) {
last = last->next;
}
*head_ref = first->next;
first->next = NULL;
last->next = first;
}
void push( struct Node** head_ref, int new_data)
{
struct Node* new_node = new Node;
new_node->data = new_data;
new_node->next = (*head_ref);
(*head_ref) = new_node;
}
void printList( struct Node* node)
{
while (node != NULL) {
printf ( "%d " , node->data);
node = node->next;
}
}
int main()
{
struct Node* start = NULL;
push(&start, 5);
push(&start, 4);
push(&start, 3);
push(&start, 2);
push(&start, 1);
printf ( "\n Linked list before moving first to end\n" );
printList(start);
moveToEnd(&start);
printf ( "\n Linked list after moving first to end\n" );
printList(start);
return 0;
}
|
Java
class Sol
{
static class Node
{
int data;
Node next;
};
static Node moveToEnd( Node head_ref)
{
if (head_ref == null || (head_ref).next == null )
return null ;
Node first = head_ref;
Node last = head_ref;
while (last.next != null )
{
last = last.next;
}
head_ref = first.next;
first.next = null ;
last.next = first;
return head_ref;
}
static Node push( Node head_ref, int new_data)
{
Node new_node = new Node();
new_node.data = new_data;
new_node.next = (head_ref);
(head_ref) = new_node;
return head_ref;
}
static void printList( Node node)
{
while (node != null )
{
System.out.printf( "%d " , node.data);
node = node.next;
}
}
public static void main(String args[])
{
Node start = null ;
start = push(start, 5 );
start = push(start, 4 );
start = push(start, 3 );
start = push(start, 2 );
start = push(start, 1 );
System.out.printf( "\n Linked list before moving first to end\n" );
printList(start);
start = moveToEnd(start);
System.out.printf( "\n Linked list after moving first to end\n" );
printList(start);
}
}
|
Python3
class Node:
def __init__( self ):
self .data = 0
self . next = None
def moveToEnd( head_ref) :
if (head_ref = = None or (head_ref). next = = None ) :
return None
first = head_ref
last = head_ref
while (last. next ! = None ) :
last = last. next
head_ref = first. next
first. next = None
last. next = first
return head_ref
def push( head_ref, new_data) :
new_node = Node()
new_node.data = new_data
new_node. next = (head_ref)
(head_ref) = new_node
return head_ref
def printList(node) :
while (node ! = None ):
print (node.data, end = " " )
node = node. next
start = None
start = push(start, 5 )
start = push(start, 4 )
start = push(start, 3 )
start = push(start, 2 )
start = push(start, 1 )
print ( "\n Linked list before moving first to end" )
printList(start)
start = moveToEnd(start)
print ( "\n Linked list after moving first to end" )
printList(start)
|
C#
using System;
class GFG
{
public class Node
{
public int data;
public Node next;
};
static Node moveToEnd( Node head_ref)
{
if (head_ref == null || (head_ref).next == null )
return null ;
Node first = head_ref;
Node last = head_ref;
while (last.next != null )
{
last = last.next;
}
head_ref = first.next;
first.next = null ;
last.next = first;
return head_ref;
}
static Node push( Node head_ref, int new_data)
{
Node new_node = new Node();
new_node.data = new_data;
new_node.next = (head_ref);
(head_ref) = new_node;
return head_ref;
}
static void printList( Node node)
{
while (node != null )
{
Console.Write( "{0} " , node.data);
node = node.next;
}
}
public static void Main(String []args)
{
Node start = null ;
start = push(start, 5);
start = push(start, 4);
start = push(start, 3);
start = push(start, 2);
start = push(start, 1);
Console.Write( "\n Linked list before moving first to end\n" );
printList(start);
start = moveToEnd(start);
Console.Write( "\n Linked list after moving first to end\n" );
printList(start);
}
}
|
Javascript
<script>
class Node
{
constructor()
{
this .data = 0;
this .next = null ;
}
}
function moveToEnd(head_ref)
{
if (head_ref == null || head_ref.next == null )
return null ;
var first = head_ref;
var last = head_ref;
while (last.next != null )
{
last = last.next;
}
head_ref = first.next;
first.next = null ;
last.next = first;
return head_ref;
}
function push(head_ref, new_data)
{
var new_node = new Node();
new_node.data = new_data;
new_node.next = head_ref;
head_ref = new_node;
return head_ref;
}
function printList(node)
{
while (node != null )
{
document.write(node.data + " " );
node = node.next;
}
}
var start = null ;
start = push(start, 5);
start = push(start, 4);
start = push(start, 3);
start = push(start, 2);
start = push(start, 1);
document.write( "Linked list before " +
"moving first to end<br>" );
printList(start);
start = moveToEnd(start);
document.write( "<br> Linked list after moving " +
"first to end<br>" );
printList(start);
</script>
|
Output
Linked list before moving first to end
1 2 3 4 5
Linked list after moving first to end
2 3 4 5 1
Time Complexity: O(n) where n is the number of nodes in the given Linked List.
Auxiliary Space: O(1)
Method: Optimized Move First Element to End of Linked List
Steps:
- If the linked list is empty or has only one element, return the same linked list.
- Store the head node in a variable and set the head to the second node.
- Traverse the linked list until the last node.
- Set the next of the last node to the original head node.
- Set the next of the original head node to None.
- Return the modified linked list.
C++
#include <iostream>
using namespace std;
class Node {
public :
int data;
Node* next;
Node( int data) {
this ->data = data;
next = nullptr;
}
};
class LinkedList {
public :
Node* head;
LinkedList() {
head = nullptr;
}
void insert( int data) {
Node* new_node = new Node(data);
if (!head) {
head = new_node;
} else {
Node* current_node = head;
while (current_node->next) {
current_node = current_node->next;
}
current_node->next = new_node;
}
}
void display() {
Node* current_node = head;
while (current_node) {
cout << current_node->data << " " ;
current_node = current_node->next;
}
cout << endl;
}
Node* move_first_to_end() {
if (!head || !head->next) {
return head;
}
Node* old_head = head;
head = head->next;
Node* current_node = head;
while (current_node->next) {
current_node = current_node->next;
}
current_node->next = old_head;
old_head->next = nullptr;
return head;
}
};
int main() {
LinkedList linked_list;
linked_list.insert(1);
linked_list.insert(2);
linked_list.insert(3);
linked_list.insert(4);
linked_list.insert(5);
cout << "Original Linked List: " ;
linked_list.display();
linked_list.move_first_to_end();
cout << "Modified Linked List: " ;
linked_list.display();
return 0;
}
|
Java
public class Main {
public static void main(String[] args) {
LinkedList linked_list = new LinkedList();
linked_list.insert( 1 );
linked_list.insert( 2 );
linked_list.insert( 3 );
linked_list.insert( 4 );
linked_list.insert( 5 );
System.out.print( "Original Linked List: " );
linked_list.display();
linked_list.move_first_to_end();
System.out.print( "Modified Linked List: " );
linked_list.display();
}
private static class Node {
public int data;
public Node next;
public Node( int data) {
this .data = data;
this .next = null ;
}
}
private static class LinkedList {
public Node head;
public LinkedList() {
this .head = null ;
}
public void insert( int data) {
Node new_node = new Node(data);
if ( this .head == null ) {
this .head = new_node;
} else {
Node current_node = this .head;
while (current_node.next != null ) {
current_node = current_node.next;
}
current_node.next = new_node;
}
}
public void display() {
Node current_node = this .head;
while (current_node != null ) {
System.out.print(current_node.data + " " );
current_node = current_node.next;
}
System.out.println();
}
public Node move_first_to_end() {
if ( this .head == null || this .head.next == null ) {
return this .head;
}
Node old_head = this .head;
this .head = this .head.next;
Node current_node = this .head;
while (current_node.next != null ) {
current_node = current_node.next;
}
current_node.next = old_head;
old_head.next = null ;
return this .head;
}
}
}
|
Python3
class Node:
def __init__( self , data):
self .data = data
self . next = None
class LinkedList:
def __init__( self ):
self .head = None
def insert( self , data):
new_node = Node(data)
if not self .head:
self .head = new_node
else :
current_node = self .head
while current_node. next :
current_node = current_node. next
current_node. next = new_node
def display( self ):
current_node = self .head
while current_node:
print (current_node.data, end = ' ' )
current_node = current_node. next
print ()
def move_first_to_end( self ):
if not self .head or not self .head. next :
return self .head
old_head = self .head
self .head = self .head. next
current_node = self .head
while current_node. next :
current_node = current_node. next
current_node. next = old_head
old_head. next = None
return self .head
linked_list = LinkedList()
linked_list.insert( 1 )
linked_list.insert( 2 )
linked_list.insert( 3 )
linked_list.insert( 4 )
linked_list.insert( 5 )
print ( "Original Linked List: " )
linked_list.display()
linked_list.move_first_to_end()
print ( "Modified Linked List: " )
linked_list.display()
|
C#
using System;
class Node
{
public int data;
public Node next;
public Node( int data)
{
this .data = data;
next = null ;
}
}
class LinkedList
{
public Node head;
public LinkedList()
{
head = null ;
}
public void insert( int data)
{
Node new_node = new Node(data);
if (head == null )
{
head = new_node;
}
else
{
Node current_node = head;
while (current_node.next != null )
{
current_node = current_node.next;
}
current_node.next = new_node;
}
}
public void display()
{
Node current_node = head;
while (current_node != null )
{
Console.Write(current_node.data + " " );
current_node = current_node.next;
}
Console.WriteLine();
}
public Node move_first_to_end()
{
if (head == null || head.next == null )
{
return head;
}
Node old_head = head;
head = head.next;
Node current_node = head;
while (current_node.next != null )
{
current_node = current_node.next;
}
current_node.next = old_head;
old_head.next = null ;
return head;
}
}
class Program
{
static void Main( string [] args)
{
LinkedList linked_list = new LinkedList();
linked_list.insert(1);
linked_list.insert(2);
linked_list.insert(3);
linked_list.insert(4);
linked_list.insert(5);
Console.Write( "Original Linked List: " );
linked_list.display();
linked_list.move_first_to_end();
Console.Write( "Modified Linked List: " );
linked_list.display();
Console.ReadLine();
}
}
|
Javascript
class Node {
constructor(data) {
this .data = data;
this .next = null ;
}
}
class LinkedList {
constructor() {
this .head = null ;
}
insert(data) {
let new_node = new Node(data);
if ( this .head == null ) {
this .head = new_node;
} else {
let current_node = this .head;
while (current_node.next != null ) {
current_node = current_node.next;
}
current_node.next = new_node;
}
}
display() {
let current_node = this .head;
while (current_node != null ) {
console.log(current_node.data + " " );
current_node = current_node.next;
}
console.log();
}
move_first_to_end() {
if ( this .head == null || this .head.next == null ) {
return this .head;
}
let old_head = this .head;
this .head = this .head.next;
let current_node = this .head;
while (current_node.next != null ) {
current_node = current_node.next;
}
current_node.next = old_head;
old_head.next = null ;
return this .head;
}
}
let linked_list = new LinkedList();
linked_list.insert(1);
linked_list.insert(2);
linked_list.insert(3);
linked_list.insert(4);
linked_list.insert(5);
console.log( "Original Linked List: " );
linked_list.display();
linked_list.move_first_to_end();
console.log( "Modified Linked List: " );
linked_list.display();
|
Output
Original Linked List:
1 2 3 4 5
Modified Linked List:
2 3 4 5 1
Time complexity: O(n)
Auxiliary space: O(1)
Last Updated :
19 Apr, 2023
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