Insert Node at the End of a Linked List

Last Updated : 29 Jul, 2024

Given a linked list, the task is to insert a new node at the end of the linked list.

Examples:

Input: LinkedList = 2 -> 3 -> 4 -> 5, NewNode = 1
Output: LinkedList = 2 -> 3 -> 4 -> 5 -> 1
Input: LinkedList = NULL, NewNode = 1
Output: LinkedList = 1

Approach:

Inserting at the end involves traversing the entire list until we reach the last node. We then set the last node's next reference to point to the new node, making the new node the last element in the list.

Insertion-at-the-End-of-Singly-Linked-List

Following is the approach to add a new node at the end of the linked list:

Create a new node and set its next pointer as NULL since it will be the last node.
Store the head reference in a temporary variable
If the Linked List is empty, make the new node as the head and return
Else traverse till the last node
Change the next pointer of the last node to point to the new node

Below is the implementation of the approach:

C++

#include <iostream> using namespace std;  // A linked list node class Node { public:     int data;     Node* next;      // Constructor to initialize a new node with data     Node(int new_data) {         data = new_data;         next = nullptr;     } };  // Given the head of a list and an int, appends // a new node at the end and returns the head. Node* append(Node* head, int new_data) {        // Create a new node     Node* new_node = new Node(new_data);      // If the Linked List is empty, make     // the new node as the head and return     if (head == nullptr) {         return new_node;     }      // Store the head reference in a temporary variable     Node* last = head;      // Traverse till the last node     while (last->next != nullptr) {         last = last->next;     }      // Change the next pointer of the last node      // to point to the new node     last->next = new_node;      // Return the head of the list     return head; }  // This function prints the contents  // of the linked list starting from the head void printList(Node* node) {     while (node != nullptr) {         cout << " " << node->data;         node = node->next;     } }  // Driver code int main() {        // Create a hard-coded linked list:     // 2 -> 3 -> 4 -> 5 -> 6     Node* head = new Node(2);     head->next = new Node(3);     head->next->next = new Node(4);     head->next->next->next = new Node(5);     head->next->next->next->next = new Node(6);      cout << "Created Linked list is:";     printList(head);      // Example of appending a node at the end     head = append(head, 1);      cout << "\nAfter inserting 1 at the end:";     printList(head);      return 0; }

#include <stdio.h> #include <stdlib.h>  // A linked list node struct Node {     int data;     struct Node* next; };  // Function to create a new node struct Node* createNode(int new_data) {     struct Node* new_node =         (struct Node*)malloc(sizeof(struct Node));     new_node->data = new_data;     new_node->next = NULL;     return new_node; }  // Given the head of a list and an int, appends // a new node at the end and returns the head. struct Node* append(struct Node* head, int new_data) {        // Create a new node     struct Node* new_node = createNode(new_data);      // If the Linked List is empty, make     // the new node as the head and return     if (head == NULL) {         return new_node;     }      // Store the head reference in a temporary variable     struct Node* last = head;      // Traverse till the last node     while (last->next != NULL) {         last = last->next;     }      // Change the next pointer of the last node      // to point to the new node     last->next = new_node;      // Return the head of the list     return head; }  // This function prints the contents  // of the linked list starting from the head void printList(struct Node* node) {     while (node != NULL) {         printf(" %d", node->data);         node = node->next;     } }  // Driver code int main() {        // Create a hard-coded linked list:      // 2 -> 3 -> 4 -> 5 -> 6     struct Node* head = createNode(2);     head->next = createNode(3);     head->next->next = createNode(4);     head->next->next->next = createNode(5);     head->next->next->next->next = createNode(6);      printf("Created Linked list is:");     printList(head);      // Example of appending a node at the end     head = append(head, 1);      printf("\nAfter inserting 1 at the end:");     printList(head);      return 0; }

Java

class Node {     int data;     Node next;      // Constructor to initialize a new node with data     Node(int newData) {         data = newData;         next = null;     } }  public class GfG {          // Given the head of a list and an int, appends     // a new node at the end and returns the head.     static Node append(Node head, int newData) {                // Create a new node         Node newNode = new Node(newData);          // If the Linked List is empty, make the new          // node as the head and return         if (head == null) {             return newNode;         }          // Store the head reference in a temporary variable         Node last = head;          // Traverse till the last node         while (last.next != null) {             last = last.next;         }          // Change the next pointer of the          // last node to point to the new node         last.next = newNode;          // Return the head of the list         return head;     }      // This function prints the contents of      // the linked list starting from the head     public static void printList(Node node) {         while (node != null) {             System.out.print(" " + node.data);             node = node.next;         }     }      // Driver code     public static void main(String[] args) {                // Create a hard-coded linked list:          // 2 -> 3 -> 4 -> 5 -> 6         Node head = new Node(2);         head.next = new Node(3);         head.next.next = new Node(4);         head.next.next.next = new Node(5);         head.next.next.next.next = new Node(6);          System.out.print("Created Linked list is:");         printList(head);          // Example of appending a node at the end         head = append(head, 1);          System.out.print("\nAfter inserting 1 at the end:");         printList(head);     } }

Python

class Node:     def __init__(self, data):         self.data = data         self.next = None   # Given the head of a list and an int, appends # a new node at the end and returns the head. def append(head, new_data):      # Create a new node     new_node = Node(new_data)      # If the Linked List is empty, make the      # new node as the head and return     if head is None:         return new_node      # Store the head reference in a temporary variable     last = head      # Traverse till the last node     while last.next:         last = last.next      # Change the next pointer of the last      # node to point to the new node     last.next = new_node      # Return the head of the list     return head   # This function prints the contents of the  # linked list starting from the head def print_list(node):      while node:         print(node.data, end=" ")         node = node.next   # Driver code if __name__ == "__main__":      # Create a hard-coded linked list:      # 2 -> 3 -> 4 -> 5 -> 6     head = Node(2)     head.next = Node(3)     head.next.next = Node(4)     head.next.next.next = Node(5)     head.next.next.next.next = Node(6)      print("Created Linked list is: ", end="")     print_list(head)      # Example of appending a node at the end     head = append(head, 1)      print("\nAfter inserting 1 at the end: ", end="")     print_list(head)

using System;  public class Node {     public int data;     public Node next;      // Constructor to initialize a new node with data     public Node(int newData)     {         data = newData;         next = null;     } }  // Appends a new node at the end  // and returns the head. public class GfG {     public static Node Append(Node head, int newData)     {         // Create a new node         Node newNode = new Node(newData);          // If the Linked List is empty,         // make the new node as the head         if (head == null)         {             return newNode;         }          // Store the head reference in a          // temporary variable         Node last = head;          // Traverse till the last node         while (last.next != null)         {             last = last.next;         }          // Change the next pointer of the          // last node to point to the new node         last.next = newNode;          // Return the head of the list         return head;     }      // Prints the contents of the linked     // list starting from the head     public static void PrintList(Node node)     {         while (node != null)         {             Console.Write(node.data + " ");             node = node.next;         }     }      // Driver code     public static void Main(string[] args)     {         // Create a hard-coded linked list:         // 2 -> 3 -> 4 -> 5 -> 6         Node head = new Node(2);         head.next = new Node(3);         head.next.next = new Node(4);         head.next.next.next = new Node(5);         head.next.next.next.next = new Node(6);          Console.Write("Created Linked list is: ");         PrintList(head);          // Example of appending a node          // at the end         head = Append(head, 1);          Console.Write("\nAfter inserting 1 at the end: ");         PrintList(head);     } }

JavaScript

class Node {     constructor(data) {         this.data = data;         this.next = null;     } }  // Appends a new node at the end  // and returns the head. function append(head, newData) {      // Create a new node     const newNode = new Node(newData);      // If the Linked List is empty,     // make the new node as the head     if (head === null) {         return newNode;     }      // Store the head reference in a      // temporary variable     let last = head;      // Traverse till the last node     while (last.next !== null) {         last = last.next;     }      // Change the next pointer of the      // last node to point to the new node     last.next = newNode;      // Return the head of the list     return head; }  // Prints the contents of the linked // list starting from the head function printList(node) {     while (node !== null) {         console.log(node.data + " ");         node = node.next;     } }  // Create a hard-coded linked list: // 2 -> 3 -> 4 -> 5 -> 6 let head = new Node(2); head.next = new Node(3); head.next.next = new Node(4); head.next.next.next = new Node(5); head.next.next.next.next = new Node(6);  console.log("Created Linked list is:"); printList(head);  // Example of appending a node  // at the end head = append(head, 1);  console.log("\nAfter inserting 1 at the end:"); printList(head);

Output

Created Linked list is:  2 3 4 5 6 After inserting 1 at the end:  2 3 4 5 6 1

Time Complexity: O(N) where N is the length of the linked list
Auxiliary Space: O(1)

Insert a Node at the end of Doubly Linked List

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Insert Node at the End of a Linked List

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