Insert a Node after a given Node in Linked List
Like arrays, Linked List is a linear data structure. Unlike arrays, linked list elements are not stored at a contiguous location; the elements are linked using pointers. They include a series of connected nodes. Here, each node stores the data and the address of the next node.
To learn more about linked list refer to the article “Introduction to Linked LIst“.
Given a linked list, the task is to insert a new node after a given node of the linked list.
Insert new node after a given node in linked list
Example:
List = 1->2->4->5, Insert a node with value 3 after the node with value 2.
Output list will be: 1->2->3->4->5
Consider the following representations of the linked list.
C++
// A linked list node
class Node {
public:
int data;
Node* next;
};
C
// A linked list node
struct Node {
int data;
struct Node* next;
};
Java
// Linked List Class
class LinkedList {
Node head; // head of list
/* Node Class */
class Node {
int data;
Node next;
// Constructor to create a new node
Node(int d)
{
data = d;
next = null;
}
}
}
Python3
# Node class
class Node:
# Function to initialize the node object
def __init__(self, data):
self.data = data # Assign data
self.next = None # Initialize next as null
# Linked List class
class LinkedList:
# Function to initialize the Linked List object
def __init__(self):
self.head = None
C#
/* Linked list Node*/
public class Node {
public int data;
public Node next;
public Node(int d)
{
data = d;
next = null;
}
}
Javascript
<script>
// Linked List Class
var head; // head of list
/* Node Class */
class Node {
// Constructor to create a new node
constructor(d) {
this.data = d;
this.next = null;
}
}
// This code is contributed by todaysgaurav
</script>
Approach: Follow the below steps for inserting a node after a given node:
- Firstly, check if the given previous node is NULL or not.
- Then, allocate a new node (say temp) and
- Assign the data to temp.
- And then make the next of temp as the next of the previous node.
- Finally, move the next of the previous node to point to temp.
Follow the below image for a better understanding.
How to insert a new node after given node in linked list
Below is the implementation of the approach.
C++
// Given a node prev_node, insert a
// new node after the given
// prev_node
void insertAfter(Node* prev_node, int new_data)
{
// 1. Check if the given prev_node is NULL
if (prev_node == NULL) {
cout << "The given previous node cannot be NULL";
return;
}
// 2. Allocate new node
Node* new_node = new Node();
// 3. Put in the data
new_node->data = new_data;
// 4. Make next of new node as
// next of prev_node
new_node->next = prev_node->next;
// 5. move the next of prev_node
// as new_node
prev_node->next = new_node;
}
C
/* Given a node prev_node, insert a new node after the given
prev_node */
void insertAfter(struct Node* prev_node, int new_data)
{
/*1. check if the given prev_node is NULL */
if (prev_node == NULL) {
printf("the given previous node cannot be NULL");
return;
}
/* 2. allocate new node */
struct Node* new_node
= (struct Node*)malloc(sizeof(struct Node));
/* 3. put in the data */
new_node->data = new_data;
/* 4. Make next of new node as next of prev_node */
new_node->next = prev_node->next;
/* 5. move the next of prev_node as new_node */
prev_node->next = new_node;
}
Java
/* This function is in LinkedList class.
Inserts a new node after the given prev_node. This method is
defined inside LinkedList class shown above */
public void insertAfter(Node prev_node, int new_data)
{
/* 1. Check if the given Node is null */
if (prev_node == null) {
System.out.println(
"The given previous node cannot be null");
return;
}
/* 2. Allocate the Node &
3. Put in the data*/
Node new_node = new Node(new_data);
/* 4. Make next of new Node as next of prev_node */
new_node.next = prev_node.next;
/* 5. make next of prev_node as new_node */
prev_node.next = new_node;
}
Python3
# This function is in LinkedList class.
# Inserts a new node after the given prev_node. This method is
# defined inside LinkedList class shown above */
def insertAfter(self, prev_node, new_data):
# 1. check if the given prev_node exists
if prev_node is None:
print("The given previous node must inLinkedList.")
return
# 2. Create new node &
# 3. Put in the data
new_node = Node(new_data)
# 4. Make next of new Node as next of prev_node
new_node.next = prev_node.next
# 5. make next of prev_node as new_node
prev_node.next = new_node
C#
/* Inserts a new node after the given prev_node. */
public void insertAfter(Node prev_node, int new_data)
{
/* 1. Check if the given Node is null */
if (prev_node == null) {
Console.WriteLine("The given previous node"
+ " cannot be null");
return;
}
/* 2 & 3: Allocate the Node &
Put in the data*/
Node new_node = new Node(new_data);
/* 4. Make next of new Node as
next of prev_node */
new_node.next = prev_node.next;
/* 5. make next of prev_node
as new_node */
prev_node.next = new_node;
}
Javascript
<script>
/* This function is in LinkedList class.
Inserts a new node after the given prev_node. This method is
defined inside LinkedList class shown above */
function insertAfter(prev_node, new_data)
{
/* 1. Check if the given Node is null */
if (prev_node == null)
{
document.write("The given previous node cannot be null");
return;
}
/* 2. Allocate the Node &
3. Put in the data*/
var new_node = new Node(new_data);
/* 4. Make next of new Node as next of prev_node */
new_node.next = prev_node.next;
/* 5. make next of prev_node as new_node */
prev_node.next = new_node;
}
// This code is contributed by aashish1995
</script>
Time Complexity: O(1)
Auxiliary Space: O(1)
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