# Program To Insert A New Node At The Beginning Of The Singly Linked List

Program To Insert A New Node At The Beginning Of The Singly Linked List on fibonacci, factorial, prime, armstrong, swap, reverse, search, sort, stack, queue, array, linkedlist, tree, graph etc.

## Program to insert a new node at the beginning of the singly linked list

### Explanation

In this program, we will create a singly linked list and add a new node at the beginning of the list. To accomplish this task, we will store head to a temporary node temp. Make newly added node as the new head of the list. Then, add temp (old head) after new head.

Consider the above list; node 1 represents the head of the original list. Let node New be the new node which needs to be added at the beginning of the list. Node temp will point to head, i.e. 1. Make New as the new head of the list and add temp after new head such that node next to New will be 1.

### Algorithm

1. Create a class Node which has two attributes: data and next. Next is a pointer to the next node in the list.
2. Create another class InsertStart which has two attributes: head and tail.
3. addAtStart() will add a new node to the beginning of the list:
1. It first checks, whether the head is equal to null which means the list is empty.
2. If the list is empty, both head and tail will point to a newly added node.
3. If the list is not empty then, create temporary node temp will point to head.
4. display() will display the nodes present in the list:
1. Define a node current which will initially point to the head of the list.
2. Traverse through the list till current points to null.
3. Display each node by making current to point to node next to it in each iteration.

### Python

```#Represent a node of the singly linked list
class Node:
def __init__(self,data):
self.data = data;
self.next = None;

class InsertStart:
def __init__(self):
self.tail = None;

#addAtStart() will add a new node to the beginning of the list
#Create a new node
newNode = Node(data);

#Checks if the list is empty
#If list is empty, both head and tail will point to new node
self.tail = newNode;
else:
#Node temp will point to head
#newNode will become new head of the list

#display() will display all the nodes present in the list
def display(self):
#Node current will point to head

print("List is empty");
return;

print("Adding nodes to the start of the list: ");
while(current != None):
#Prints each node by incrementing pointer
print(current.data ),
current = current.next;

sList = InsertStart();

sList.display();
sList.display();
sList.display();
sList.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>

//Represent a node of the singly linked list
struct node{
int data;
struct node *next;
};

struct node *head, *tail = NULL;

//addAtStart() will add a new node to the beginning of the list
//Create a new node
struct node *newNode = (struct node*)malloc(sizeof(struct node));
newNode->data = data;
newNode->next = NULL;

//Checks if the list is empty
//If list is empty, both head and tail will point to new node
tail = newNode;
}
else {
//Node temp will point to head
//newNode will become new head of the list
}
}

//display() will display all the nodes present in the list
void display() {
//Node current will point to head

printf("List is empty\n");
return;
}
printf("Adding nodes to the start of the list: \n");
while(current != NULL) {
//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 InsertStart {

//Represent a node of the singly linked list
class Node{
int data;
Node next;

public Node(int data) {
this.data = data;
this.next = null;
}
}

public Node tail = null;

//addAtStart() will add a new node to the beginning of the list
//Create a new node
Node newNode = new Node(data);

//Checks if the list is empty
//If list is empty, both head and tail will point to new node
tail = newNode;
}
else {
//Node temp will point to head
//newNode will become new head of the list
}
}

//display() will display all the nodes present in the list
public void display() {
//Node current will point to head
System.out.println("List is empty");
return;
}
System.out.println("Adding nodes to the start of the list: ");
while(current != null) {
//Prints each node by incrementing pointer
System.out.print(current.data + " ");
current = current.next;
}
System.out.println();
}

public static void main(String[] args) {

InsertStart sList = new InsertStart();

sList.display();

sList.display();

sList.display();

sList.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 CreateList
{
//Represent a node of the singly linked list
public class Node<T>{
public T data;
public Node<T> next;

public Node(T value) {
data = value;
next = null;
}
}

public class InsertStart<T>{
public Node<T> tail = null;

//addAtStart() will add a new node to the beginning of the list
//Create a new node
Node<T> newNode = new Node<T>(data);

//Checks if the list is empty
//If list is empty, both head and tail will point to new node
tail = newNode;
}
else {
//Node temp will point to head
//newNode will become new head of the list
}
}

//display() will display all the nodes present in the list
public void display() {
//Node current will point to head

Console.WriteLine("List is empty");
return;
}
Console.WriteLine("Adding nodes to the start of the list: ");
while(current != null) {
//Prints each node by incrementing pointer
Console.Write(current.data + " ");
current = current.next;
}
Console.WriteLine();
}
}

public static void Main()
{
InsertStart<int> sList = new InsertStart<int>();

sList.display();

sList.display();

sList.display();

sList.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
//Represent a node of singly linked list
class Node{
public \$data;
public \$next;

function __construct(\$data){
\$this->data = \$data;
\$this->next = NULL;
}
}
class InsertStart{
public \$tail;
function __construct(){
\$this->tail = NULL;
}

//addAtStart() will add a new node to the beginning of the list
//Create a new node
\$newNode = new Node(\$data);

//Checks if the list is empty
//If list is empty, both head and tail will point to new node
\$this->tail = \$newNode;
}
else {
//Node temp will point to head
//newNode will become new head of the list
}
}

//display() will display all the nodes present in the list
function display() {
//Node current will point to head

print("List is empty <br>");
return;
}
print("Adding nodes to the start of the list: <br>");
while(\$current != NULL) {
//Prints each node by incrementing pointer
print(\$current->data . " ");
\$current = \$current->next;
}
print("<br>");
}
}

\$sList = new InsertStart();

\$sList->display();

\$sList->display();

\$sList->display();

\$sList->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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