# Program to Insert a New Node at the Beginning of the Circular Linked List

Program to Insert a New Node at the Beginning of the Circular Linked List on fibonacci, factorial, prime, armstrong, swap, reverse, search, sort, stack, queue, array, linkedlist, tree, graph etc.

## Q. Program to insert a new node at the beginning of the circular linked list.

### Explanation

In this program, we will create a circular linked list and insert every new node at the beginning of the list. If the list is empty, then head and tail will point to the newly added node. If the list is not empty, then we will store the data of the head into a temporary node temp and make new node as the head. This new head will point to the temporary node. In simple words, the newly added node will be the first node(head) and previous head(temp) will become the second node of the list.

After inserting new node to the beginning of the list

New represents the newly added node. Earlier A was the head of the list. When new is added to the beginning of the list, new will become the new head, and it will point to the previous head, i.e., A.

### Algorithm

1. Define a Node class which represents a node in the list. It has two properties data and next which will point to the next node.
2. Define another class for creating the circular linked list and it has two nodes: head and tail. It has two methods: addAtStart() and display() .
3. addAtStart() will add the node to the beginning of the list:
1. It first checks whether the head is null (empty list), then it will insert the node as the head.
3. If the list is not empty, then the newly added node will become the new head, and it will point to previous head.
4. display() will show all the nodes present in the list.
1. Define a new node 'current' that will point to the head.
2. Print current.data till current will points to head again.
3. Current will point to the next node in the list in each iteration.

## Solution

### Python

#Represents the node of list.
class Node:
def __init__(self,data):
self.data = data;
self.next = None;

class CreateList:
#Declaring head and tail pointer as null.
def __init__(self):
self.tail = Node(None);

#This function will add at the start of the list.
newNode = Node(data);
#Checks if the list is empty.
#If list is empty, both head and tail would point to new node.
self.tail = newNode;
else:
#Store data into temporary node
#New node will point to temp as next node
newNode.next = temp;
#New node will be the head node

#Displays all the nodes in the list
def display(self):
print("List is empty");
return;
else:
print("Adding nodes to the start of the list: ");
#Prints each node by incrementing pointer.
print(current.data),
current = current.next;
print(current.data),
print("\n");

cl = CreateList();

cl.display();
cl.display();
cl.display();
cl.display();

Output:

Adding nodes to the start of the list:
1
Adding nodes to the start of the list:
2 1
Adding nodes to the start of the list:
3 2 1
Adding nodes to the start of the list:
4 3 2 1

### C

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

//Represents the node of list.
struct node{
int data;
struct node *next;
};

//Declaring head and tail pointer as null.
struct node *tail = NULL;

//This function will add the new node to the start of the list.
//Create new node
struct node *newNode = (struct node*)malloc(sizeof(struct node));
newNode->data = data;
//Checks if the list is empty.
//If list is empty, both head and tail would point to new node.
tail = newNode;
}
else {
//Store data into temporary node
//New node will point to temp as next node
newNode->next = temp;
//New node will be the head node
}
}

//This function will display the nodes of circular linked list
void display(){
printf("List is empty");
}
else{
printf("Adding nodes to the start of the list: \n");
do{
//Prints each node by incrementing pointer.
printf("%d ", current->data);
current = current->next;
printf("\n");
}
}

int main()
{
display();
display();
display();
display();

return 0;
}

Output:

Adding nodes to the start of the list:
1
Adding nodes to the start of the list:
2 1
Adding nodes to the start of the list:
3 2 1
Adding nodes to the start of the list:
4 3 2 1

### JAVA

public class InsertAtStart {
//Represents the node of list.
public class Node{
int data;
Node next;
public Node(int data) {
this.data = data;
}
}

//Declaring head and tail pointer as null.
public Node tail = null;

//This function will add the new node at the end of the list.
//Create new node
Node newNode = new Node(data);
//Checks if the list is empty.
//If list is empty, both head and tail would point to new node.
tail = newNode;
}
else {
//Store data into temporary node
//New node will point to temp as next node
newNode.next = temp;
//New node will be the head node
}
}

//Displays all the nodes in the list
public void display() {
System.out.println("List is empty");
}
else {
System.out.println("Adding nodes to the start of the list: ");
do{
//Prints each node by incrementing pointer.
System.out.print(" "+ current.data);
current = current.next;
System.out.println();
}
}

public static void main(String[] args) {
InsertAtStart cl = new InsertAtStart();

cl.display();
cl.display();
cl.display();
cl.display();
}
}

Output:

Adding nodes to the start of the list:
1
Adding nodes to the start of the list:
2 1
Adding nodes to the start of the list:
3 2 1
Adding nodes to the start of the list:
4 3 2 1

### C#

using System;
{
public class Program
{
//Represents the node of list.
public class Node<T>{
public T data;
public Node<T> next;
public Node(T value) {
data = value;
next = null;
}
}

public class CreateList<T>{
protected Node<T> tail = null;

//This function will add the new node to the start of the list.
//Create new node
Node<T> newNode = new Node<T>(data);
//Checks if the list is empty.
tail = newNode;

}else{

//Store data into temporary node
//New node will point to temp as next node
newNode.next = temp;
//New node will be the head node
}

}
//Displays all the nodes in the list
public void display(){
Console.WriteLine("List is empty");
}
else{
Console.WriteLine("Adding nodes to the start of the list: ");
do{
//Prints each node by incrementing pointer.
Console.Write(" "+ current.data);
current = current.next;

Console.WriteLine();
}
}
}

public static void Main()
{

CreateList<int> cl = new CreateList<int>();

cl.display();
cl.display();
cl.display();
cl.display();

}
}
}

Output:

Adding nodes to the start of the list:
1
Adding nodes to the start of the list:
2 1
Adding nodes to the start of the list:
3 2 1
Adding nodes to the start of the list:
4 3 2 1

### PHP

<!DOCTYPE html>
<html>
<body>
<?php
//Represents the node of list.
class Node{
public \$data;
public \$next;
function __construct(\$data){
\$this->data = \$data;
\$this->next = NULL;
}
}
class CreateList{
//Declaring head and tail pointer as null.
private \$tail;
function __construct(){
\$this->tail = NULL;
}
//This function will add the new node at the start of the list.
//Create new node
\$newNode = new Node(\$data);
//Checks if the list is empty.
//If list is empty, both head and tail would point to new node.
\$this->tail = \$newNode;
}
else{
//Store data into temporary node
//New node will point to temp as next node
\$newNode->next = \$temp;
//New node will be the head node
}
}
//Displays all the nodes in the list
function display() {
echo "List is empty";
}
else {
echo "Adding nodes to the start of the list: <br>";
do{
echo(" \$current->data");
\$current = \$current->next;
echo "<br>";
}
}
}
\$cl = new CreateList();
\$cl->display();
\$cl->display();
\$cl->display();
\$cl->display();
?>
</body>
</html>

Output:

Adding nodes to the start of the list:
1
Adding nodes to the start of the list:
2 1
Adding nodes to the start of the list:
3 2 1
Adding nodes to the start of the list:
4 3 2 1

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