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

Last Updated : 30 Jul, 2024

Given a linked list, the task is to delete the last node of the given linked list.

**Examples:

**Input: 1 -> 2 -> 3 -> 4 -> 5 -> NULL
**Output: 1 -> 2 -> 3 -> 4 -> NULL
**Explanation: The last node of the linked list is 5, so 5 is deleted.

**Input: 3 -> 12 -> 15-> NULL
**Output: 3 -> 12 -> NULL
**Explanation: The last node of the linked list is 15, so 15 is deleted.

**Approach:

To perform the deletion operation at the end of linked list, we need to traverse the list to find the **second last node, then set its next pointer to **null. If the list is empty then there is no node to delete or has only one node then point **head to **null.

Deletion-At-End

Deletion at the end of linked list

Step-by-step approach:

Check if list is empty then return **NULL.
If the list has only one node then delete it and return **NULL.
Traverse the list to find the second last node.
- Set the next pointer of **second last node to **NULL.

**Implementation:

C++ `

// C++ program to delete the last node of linked list #include using namespace std;

// Node structure for the linked list struct Node { int data; Node* next; Node(int data) : data(data) , next(nullptr) { } };

// Function to remove the last node // of the linked list Node* removeLastNode(struct Node* head) { // If the list is empty, return nullptr if (head == nullptr) { return nullptr; }

// If the list has only one node, delete it and return
// nullptr
if (head->next == nullptr) {
    delete head;
    return nullptr;
}

// Find the second last node
Node* second_last = head;
while (second_last->next->next != nullptr) {
    second_last = second_last->next;
}

// Delete the last node
delete (second_last->next);

// Change next of second last
second_last->next = nullptr;

return head;

}

void printList(Node* head) { while (head != nullptr) { cout << head->data << " -> "; head = head->next; } cout << "nullptr" << endl; }

// Driver code int main() { // Creating a static linked list // 1 -> 2 -> 3 -> 4 -> 5 -> nullptr Node* head = new Node(1); head->next = new Node(2); head->next->next = new Node(3); head->next->next->next = new Node(4); head->next->next->next->next = new Node(5);

cout << "Original list: ";
printList(head);

// Removing the last node
head = removeLastNode(head);

cout << "List after removing the last node: ";
printList(head);


return 0;

}

C

// C program to delete the last node of linked list

#include <stdio.h> #include <stdlib.h>

// Node structure for the linked list struct Node { int data; struct Node* next; };

// Function to create a new node struct Node* createNode(int data) { struct Node* newNode = (struct Node*)malloc(sizeof(struct Node)); newNode->data = data; newNode->next = NULL; return newNode; }

// Function to remove the last node of the linked list struct Node* removeLastNode(struct Node* head) { // If the list is empty, return NULL if (head == NULL) { return NULL; }

// If the list has only one node, delete it and return
// NULL
if (head->next == NULL) {
    free(head);
    return NULL;
}

// Find the second last node
struct Node* second_last = head;
while (second_last->next->next != NULL) {
    second_last = second_last->next;
}

// Delete the last node
free(second_last->next);

// Change next of second last
second_last->next = NULL;

return head;

}

// Function to print linked list void printList(struct Node* head) { while (head != NULL) { printf("%d -> ", head->data); head = head->next; } printf("NULL\n"); }

// Driver code int main() { // Creating a static linked list // 1 -> 2 -> 3 -> 4 -> 5 -> NULL struct Node* head = createNode(1); head->next = createNode(2); head->next->next = createNode(3); head->next->next->next = createNode(4); head->next->next->next->next = createNode(5);

printf("Original list: ");
printList(head);

// Removing the last node
head = removeLastNode(head);

printf("List after removing the last node: ");
printList(head);

return 0;

}

Java

// C program to delete the last node of linked list

// Node structure for the linked list class Node { int data; Node next;

Node(int data)
{
    this.data = data;
    this.next = null;
}

}

public class GFG {

// Function to remove the last node of the linked list
public static Node removeLastNode(Node head)
{

    // If the list is empty, return null
    if (head == null) {
        return null;
    }

    // If the list has only one node, delete it and
    // return null
    if (head.next == null) {
        return null;
    }

    // Find the second last node
    Node secondLast = head;
    while (secondLast.next.next != null) {
        secondLast = secondLast.next;
    }

    // Delete the last node
    secondLast.next = null;

    return head;
}

// Function to print the linked list
public static void printList(Node head)
{
    while (head != null) {
        System.out.print(head.data + " -> ");
        head = head.next;
    }
    System.out.println("null");
}

// Driver code
public static void main(String[] args)
{

    // Creating a static linked list
    // 1 -> 2 -> 3 -> 4 -> 5 -> null
    Node head = new Node(1);
    head.next = new Node(2);
    head.next.next = new Node(3);
    head.next.next.next = new Node(4);
    head.next.next.next.next = new Node(5);

    System.out.println("Original list: ");
    printList(head);

    // Removing the last node
    head = removeLastNode(head);

    System.out.println(
        "List after removing the last node: ");
    printList(head);
}

}

Python

Python program to delete the last node of linked list

Node structure for the linked list

class Node: def init(self, data): self.data = data self.next = None

Function to remove the last node of the linked list

def remove_last_node(head): # If the list is empty, return None if not head: return None

# If the list has only one node, delete it and return None
if not head.next:
    return None

# Find the second last node
second_last = head
while second_last.next.next:
    second_last = second_last.next

# Delete the last node
second_last.next = None

return head

Function to print the linked list

def print_list(head): while head: print(head.data, end=" -> ") head = head.next print("None")

Driver code

if name == "main":

# Creating a static linked list
# 1 -> 2 -> 3 -> 4 -> 5 -> None
head = Node(1)
head.next = Node(2)
head.next.next = Node(3)
head.next.next.next = Node(4)
head.next.next.next.next = Node(5)

print("Original list: ")
print_list(head)

# Removing the last node
head = remove_last_node(head)

print("List after removing the last node: ")
print_list(head)

C#

// C# program to delete the last node of linked list

using System;

// Node structure for the linked list public class Node { public int data; public Node next;

public Node(int data)
{
    this.data = data;
    this.next = null;
}

}

public class LinkedList {

// Function to remove the last node of the linked list
public static Node RemoveLastNode(Node head)
{
    // If the list is empty, return null
    if (head == null) {
        return null;
    }

    // If the list has only one node, delete it and
    // return null
    if (head.next == null) {
        return null;
    }

    // Find the second last node
    Node secondLast = head;
    while (secondLast.next.next != null) {
        secondLast = secondLast.next;
    }

    // Delete the last node
    secondLast.next = null;

    return head;
}

// Function to print the linked list
public static void PrintList(Node head)
{
    while (head != null) {
        Console.Write(head.data + " -> ");
        head = head.next;
    }
    Console.WriteLine("null");
}

// Driver code
public static void Main(string[] args)
{
    // Creating a static linked list
    // 1 -> 2 -> 3 -> 4 -> 5 -> null
    Node head = new Node(1);
    head.next = new Node(2);
    head.next.next = new Node(3);
    head.next.next.next = new Node(4);
    head.next.next.next.next = new Node(5);

    Console.WriteLine("Original list: ");
    PrintList(head);

    // Removing the last node
    head = RemoveLastNode(head);

    Console.WriteLine(
        "List after removing the last node: ");
    PrintList(head);
}

}

JavaScript

// Javascript program to delete the last node of linked list

// Node structure for the linked list class Node { constructor(data) { this.data = data; this.next = null; } }

// Function to remove the last node of the linked list function removeLastNode(head) { // If the list is empty, return null if (!head) { return null; }

// If the list has only one node, delete it and return null
if (!head.next) {
    return null;
}

// Find the second last node
let secondLast = head;
while (secondLast.next.next) {
    secondLast = secondLast.next;
}

// Delete the last node
secondLast.next = null;

return head;

}

// Function to print the linked list function printList(head) { while (head) { process.stdout.write(head.data + " -> "); head = head.next; } console.log("null"); }

// Driver code // Creating a static linked list // 1 -> 2 -> 3 -> 4 -> 5 -> null let head = new Node(1); head.next = new Node(2); head.next.next = new Node(3); head.next.next.next = new Node(4); head.next.next.next.next = new Node(5);

console.log("Original list: "); printList(head);

// Removing the last node head = removeLastNode(head);

console.log("List after removing the last node: "); printList(head);

Output

Original list: 1 -> 2 -> 3 -> 4 -> 5 -> nullptr List after removing the last node: 1 -> 2 -> 3 -> 4 -> nullptr

**Time Complexity: O(n), traversal of the linked list till its end, so the time complexity required is _O(n).
**Auxiliary Space: O(1)