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

Program To Insert A New Node At The Middle 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 middle of the singly linked list

Explanation

In this program, we will create a singly linked list and add a new node at the middle of the list. To accomplish this task, we will calculate the size of the list and divide it by 2 to get the mid-point of the list where the new node needs to be inserted.

Consider the above diagram; node 1 represents the head of the original list. Let node New is the new node which needs to be added at the middle of the list. First, we calculate size which in this case is 4. So, to get the mid-point, we divide it by 2 and store it in a variable count. Node current will point to head. First, we iterate through the list till current points to mid position. Define another node temp which point to node next to current. Insert the New node between current and temp.

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 InsertMid which has three attributes: head, tail, and size that keep tracks of a number of nodes present in the list.
3. addNode() will add a new node to the list:
1. Create a new node.
2. It first checks, whether the head is equal to null which means the list is empty.
3. If the list is empty, both head and tail will point to a newly added node.
4. If the list is not empty, the new node will be added to end of the list such that tail's next will point to a newly added node. This new node will become the new tail of the list.
4. addInMid() will add a new node at the middle 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 calculate the size of the list and divide it by 2 to get mid-point of the list.
4. Define node current that will iterate through the list till current will point to mid node.
5. Define another node temp which will point to node next to current.
6. The new node will be inserted after current and before temp such that current will point to the new node and the new node will point to temp.
5. 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 InsertMid:
#Represent the head and tail of the singly linked list
def __init__(self):
self.tail = None;
self.size = 0;

#addNode() will add a new node to 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:
#newNode will be added after tail such that tail's next will point to newNode
self.tail.next = newNode;
#newNode will become new tail of the list
self.tail = newNode;
#Size will count the number of nodes present in the list
self.size = self.size + 1;

#This function will add the new node at the middle of the list.
#Create a new node
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 the mid position of the list
count = (self.size//2) if(self.size % 2 == 0) else ((self.size+1)//2);
#Node temp will point to head
current = None;

#Traverse through the list till the middle of the list is reached
for i in range(0, count):
#Node current will point to temp
current = temp;
#Node temp will point to node next to it.
temp = temp.next;

#current will point to new node
current.next = newNode;
#new node will point to temp
newNode.next = temp;
self.size = self.size + 1;

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

print("List is empty");
return;

while(current != None):
#Prints each node by incrementing pointer
print(current.data)
current = current.next;

sList = InsertMid();

#Adds data to the list

print("Original list: ");
sList.display();

#Inserting node '3' in the middle
print( "Updated List: ");
sList.display();

#Inserting node '4' in the middle
print("Updated List: ");
sList.display();
```

Output:

``` Original list:
1 2
Updated List:
1 3 2
Updated List:
1 3 4 2
```

C

```#include <stdio.h>

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

int size;
//Represent the head and tail of the singly linked list
struct node *head, *tail = NULL;

//addNode() will add a new node to the list
void addNode(int data) {
//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(head == NULL) {
//If list is empty, both head and tail will point to new node
tail = newNode;
}
else {
//newNode will be added after tail such that tail's next will point to newNode
tail->next = newNode;
//newNode will become new tail of the list
tail = newNode;
}
//Size will count the number of nodes present in the list
size++;
}

//This function will add the new node at the middle 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(head == NULL) {
//If list is empty, both head and tail would point to new node
tail = newNode;
}
else {
struct node *temp, *current;
//Store the mid position of the list
int count = (size % 2 == 0) ? (size/2) : ((size+1)/2);
//Node temp will point to head
current = NULL;

//Traverse through the list till the middle of the list is reached
for(int i = 0; i < count; i++) {
//Node current will point to temp
current = temp;
//Node temp will point to node next to it.
temp = temp->next;
}

//current will point to new node
current->next = newNode;
//new node will point to temp
newNode->next = temp;
}
size++;
}

//display() will display all the nodes present in the list
void display() {
//Node current will point to head
struct node *current = head;

if(head == NULL) {
printf("List is empty\n");
return;
}
while(current != NULL) {
//Prints each node by incrementing pointer
printf("%d ", current->data);
current = current->next;
}
printf("\n");
}

int main()
{
//Adds data to the list

printf("Original list: \n");
display();

//Inserting node '3' in the middle
printf( "Updated List: \n");
display();

//Inserting node '4' in the middle
printf("Updated List: \n");
display();

return 0;
}
```

Output:

```Original list:
1 2
Updated List:
1 3 2
Updated List:
1 3 4 2
```

JAVA

```public class InsertMid {

//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 int size;
//Represent the head and tail of the singly linked list
public Node head = null;
public Node tail = null;

//addNode() will add a new node to the list
public void addNode(int data) {
//Create a new node
Node newNode = new Node(data);

//Checks if the list is empty
if(head == null) {
//If list is empty, both head and tail will point to new node
tail = newNode;
}
else {
//newNode will be added after tail such that tail's next will point to newNode
tail.next = newNode;
//newNode will become new tail of the list
tail = newNode;
}
//Size will count the number of nodes present in the list
size++;
}

//This function will add the new node at the middle of the list.
public void addInMid(int data){
//Create a new node
Node newNode = new Node(data);

//Checks if the list is empty
if(head == null) {
//If list is empty, both head and tail would point to new node
tail = newNode;
}
else {
Node temp, current;
//Store the mid position of the list
int count = (size % 2 == 0) ? (size/2) : ((size+1)/2);
//Node temp will point to head
current = null;

//Traverse through the list till the middle of the list is reached
for(int i = 0; i < count; i++) {
//Node current will point to temp
current = temp;
//Node temp will point to node next to it.
temp = temp.next;
}

//current will point to new node
current.next = newNode;
//new node will point to temp
newNode.next = temp;
}
size++;
}

//display() will display all the nodes present in the list
public void display() {
//Node current will point to head
Node current = head;
if(head == null) {
System.out.println("List is empty");
return;
}

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) {

InsertMid sList = new InsertMid();

//Adds data to the list

System.out.println("Original list: ");
sList.display();

//Inserting node '3' in the middle
System.out.println( "Updated List: ");
sList.display();

//Inserting node '4' in the middle
System.out.println("Updated List: ");
sList.display();
}
}
```

Output:

```Original list:
1 2
Updated List:
1 3 2
Updated List:
1 3 4 2
```

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 InsertMid<T>{
public int size;
//Represent the head and tail of the singly linked list
public Node<T> head = null;
public Node<T> tail = null;

//addNode() will add a new node to the list
public void addNode(T data) {
//Create a new node
Node<T> newNode = new Node<T>(data);

//Checks if the list is empty
if(head == null) {
//If list is empty, both head and tail will point to new node
tail = newNode;
}
else {
//newNode will be added after tail such that tail's next will point to newNode
tail.next = newNode;
//newNode will become new tail of the list
tail = newNode;
}
//Size will count the number of nodes present in the list
size++;
}

//This function will add the new node at the middle of the list.
public void addInMid(T data){
//Create a new node
Node<T> newNode = new Node<T>(data);

//Checks if the list is empty
if(head == null) {
//If list is empty, both head and tail would point to new node
tail = newNode;
}
else {
Node<T> temp, current;
//Store the mid position of the list
int count = (size % 2 == 0) ? (size/2) : ((size+1)/2);
//Node temp will point to head
current = null;

//Traverse through the list till the middle of the list is reached
for(int i = 0; i < count; i++) {
//Node current will point to temp
current = temp;
//Node temp will point to node next to it.
temp = temp.next;
}

//current will point to new node
current.next = newNode;
//new node will point to temp
newNode.next = temp;
}
size++;
}

//display() will display all the nodes present in the list
public void display() {
//Node current will point to head
Node<T> current = head;
if(head == null) {
Console.WriteLine("List is empty");
return;
}

while(current != null) {
//Prints each node by incrementing pointer
Console.Write(current.data + " ");
current = current.next;
}
Console.WriteLine();
}
}

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

//Adds data to the list

Console.WriteLine("Original list: ");
sList.display();

//Inserting node '3' in the middle
Console.WriteLine( "Updated List: ");
sList.display();

//Inserting node '4' in the middle
Console.WriteLine("Updated List: ");
sList.display();
}
}
```

Output:

```Original list:
1 2
Updated List:
1 3 2
Updated List:
1 3 4 2
```

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 InsertMid{
//Represent the head and tail of the singly linked list
public \$tail;
function __construct(){
\$this->tail = NULL;
\$this->size = 0;
}

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

//Checks if the list is empty
if(\$this->head == null) {
//If list is empty, both head and tail will point to new node
\$this->tail = \$newNode;
}
else {
//newNode will be added after tail such that tail's next will point to newNode
\$this->tail->next = \$newNode;
//newNode will become new tail of the list
\$this->tail = \$newNode;
}
//Size will count the number of nodes present in the list
\$this->size++;
}

//This function will add the new node at the middle of the list.
//Create a new node
\$newNode = new Node(\$data);

//Checks if the list is empty
if(\$this->head == null) {
//If list is empty, both head and tail would point to new node
\$this->tail = \$newNode;
}
else {
//Store the mid position of the list
\$count = (\$this->size % 2 == 0) ? (\$this->size/2) : ((\$this->size+1)/2);
//Node temp will point to head
\$current = null;

//Traverse through the list till the middle of the list is reached
for(\$i = 0; \$i < \$count; \$i++) {
//Node current will point to temp
\$current = \$temp;
//Node temp will point to node next to it.
\$temp = \$temp->next;
}

//current will point to new node
\$current->next = \$newNode;
//new node will point to temp
\$newNode->next = \$temp;
}
\$this->size++;
}

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

if(\$this->head == NULL) {
print("List is empty <br>");
return;
}
while(\$current != NULL) {
//Prints each node by incrementing pointer
print(\$current->data . " ");
\$current = \$current->next;
}
print("<br>");
}
}

\$sList = new InsertMid();

//Adds data to the list

print("Original list: <br>");
\$sList->display();

//Inserting node '3' in the middle
print( "Updated List: <br>");
\$sList->display();

//Inserting node '4' in the middle
print("Updated List: <br>");
\$sList->display();
?>
</body>
</html>
```

Output:

```Original list:
1 2
Updated List:
1 3 2
Updated List:
1 3 4 2
```

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