Deletion at beginning (Removal of first node) in a Linked List

Last Updated : 30 Aug, 2024

Given a linked list, The task is to remove the first node from the given linked list.

Examples:

Input : head : 3 -> 12 -> 15 -> 18 -> NULL
Output : 12 -> 15 -> 18 -> NULL

Input : head : 2 -> 4 -> 6 -> 8 -> 33 -> 67 -> NULL
Output : 4 -> 6 -> 8 -> 33 -> 67 -> NULL

By Shifting head node to next node of head – O(1) Time and O(1) Space

To remove the first node of a linked list, store the current head in a temporary variable (temp), move the head pointer to the next node, delete the temporary head node and finally , return the new head of the linked list.

Deletion at beginning in a Linked List

Below is the implementation of the above approach:

C++

// C++ program to delete the head node  // from a linked list  #include <iostream> using namespace std;  struct Node {     int data;     Node *next;     Node(int x) {         data = x;         next = nullptr;     } };  // Delete the head node and return the new head Node* deleteHead(Node* head) {        // Check if the list is empty     if (head == nullptr)         return nullptr;      // Store the current head in a   	// temporary variable     Node* temp = head;      // Move the head pointer to the next node     head = head->next;      // Free the memory of the old head node     delete temp;      return head; }  void printList(Node* curr) {     while (curr != nullptr) {       	cout << curr->data << " ";         curr = curr->next;      } }  int main() {        // Create a hard-coded linked list:     // 3 -> 12 -> 15 -> 18     Node* head = new Node(3);     head->next = new Node(12);     head->next->next = new Node(15);     head->next->next->next = new Node(18);     head = deleteHead(head);     printList(head);      return 0; }

// C program to delete the head node // from a linked list  #include <stdio.h> #include <stdlib.h>  struct Node {     int data;     struct Node* next; };  // Delete the head node and return the new head struct Node* deleteHead(struct Node* head) {        // Check if the list is empty     if (head == NULL)         return NULL;      // Store the current head in a    	// temporary variable     struct Node* temp = head;      // Move the head pointer to the next node     head = head->next;      // Free the memory of the old head node     free(temp);      return head; }  void printList(struct Node* curr) {   	     while (curr != NULL) {         printf("%d ", curr->data);         curr = curr->next;     } } 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; }  int main() {        // Create a hard-coded linked list:     // 3 -> 12 -> 15 -> 18     struct Node* head = createNode(3);     head->next = createNode(12);     head->next->next = createNode(15);     head->next->next->next = createNode(18);     head = deleteHead(head);     printList(head);      return 0; }

Java

// Java program to delete the head node // from a linked list  class Node {     int data;     Node next;      Node(int data) {         this.data = data;         this.next = null;     } }  public class GfG {      // Delete the head node and return the new head     static Node deleteHead(Node head) {                // Check if the list is empty         if (head == null)             return null;          // Store the current head in a temporary variable         Node temp = head;          // Move the head pointer to the next node         head = head.next;          // Help the garbage collector by        	// removing the reference         temp = null;          return head;     }      static void printList(Node curr) {         while (curr != null) {             System.out.print(curr.data + " ");             curr = curr.next;         }     }      public static void main(String[] args) {                 // Create a hard-coded linked list:         // 3 -> 12 -> 15 -> 18         Node head = new Node(3);         head.next = new Node(12);         head.next.next = new Node(15);         head.next.next.next = new Node(18);         head = deleteHead(head);         printList(head);     } }

Python

# Python program to delete the head node  # from a linked list  class Node:     def __init__(self, data):         self.data = data         self.next = None  # Delete the head node and return the new head def delete_head(head):        # Check if the list is empty     if head is None:         return None      # Store the current head in a temporary variable     temp = head      # Move the head pointer to the next node     head = head.next      # Delete the old head by removing the reference     del temp      return head  def print_list(curr):     while curr:         print(curr.data, end=" ")         curr = curr.next  if __name__ == "__main__":         # Create a hard-coded linked list:     # 3 -> 12 -> 15 -> 18     head = Node(3)     head.next = Node(12)     head.next.next = Node(15)     head.next.next.next = Node(18)     head = delete_head(head)     print_list(head)

// C# program to delete the head node // from a linked list  using System;  class Node {     public int data;     public Node next;      public Node(int data) {         this.data = data;         this.next = null;     } }  class GfG {      // Delete the head node and return the new head     static Node DeleteHead(Node head) {                // Check if the list is empty         if (head == null)             return null;          // Move the head pointer to the next node         head = head.next;          return head;     }      static void PrintList(Node curr) {         while (curr != null) {             Console.Write(curr.data + " ");             curr = curr.next;         }     }      static void Main() {            // Create a hard-coded linked list:         // 3 -> 12 -> 15 -> 18         Node head = new Node(3);         head.next = new Node(12);         head.next.next = new Node(15);         head.next.next.next = new Node(18);         head = DeleteHead(head);         PrintList(head);     } }

JavaScript

// JavaScript program to delete the head //node from a linked list  class Node {     constructor(data) {         this.data = data;         this.next = null;     } }  // Delete the head node and return the new head function deleteHead(head) {      // Check if the list is empty     if (head === null)         return null;      // Store the current head in a temporary variable     let temp = head;      // Move the head pointer to the next node     head = head.next;      // Free the memory of the old head node     temp = null;      return head; }  function printList(curr) {     while (curr !== null) {         console.log(curr.data + " ");         curr = curr.next;     }  }  // Create a hard-coded linked list: // 3 -> 12 -> 15 -> 18 let head = new Node(3); head.next = new Node(12); head.next.next = new Node(15); head.next.next.next = new Node(18);  head = deleteHead(head); printList(head);

Output

12 15 18

Time Complexity: O(1), because the operation to delete the head node is performed in constant time.
Space Complexity: O(1)

Deletion at end (Removal of last node) in a Linked List

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Deletion at beginning (Removal of first node) in a Linked List

By Shifting head node to next node of head – O(1) Time and O(1) Space

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