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