Delete Node at End in DSA Python - Build from Scratch

Delete Node at End in a Singly Linked List

📖 Scenario: Imagine you have a list of tasks to do, written on sticky notes linked one after another. You want to remove the last task from the list because it's already done.

🎯 Goal: You will build a simple singly linked list and write code to delete the last node (task) from it.

📋 What You'll Learn

Create a singly linked list with exactly three nodes containing values 10, 20, and 30

Create a variable called head that points to the first node

Write code to delete the last node from the linked list

Print the linked list after deletion in the format: 10 -> 20 -> null

💡 Why This Matters

🌍 Real World

Linked lists are used in many applications like task scheduling, undo functionality, and managing playlists where items are added or removed dynamically.

💼 Career

Understanding linked list operations like deleting nodes is fundamental for software development roles that involve data structure manipulation and memory management.

1

Create a singly linked list with three nodes

Create a class called Node with an __init__ method that takes data and sets self.data and self.next. Then create three nodes with values 10, 20, and 30. Link them so that the first node points to the second, and the second points to the third. Finally, create a variable called head that points to the first node.

DSA Python

# Define Node class and create three linked nodes
# Your code here

Hint

Start by defining the Node class with data and next. Then create three nodes and link them.

2

Create a helper variable to track the current node

Create a variable called current and set it equal to head. This will help us move through the linked list.

DSA Python

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

node1 = Node(10)
node2 = Node(20)
node3 = Node(30)

node1.next = node2
node2.next = node3

head = node1

# Create a variable current and set it to head
# Your code here

Hint

We use current to walk through the list starting from head.

3

Delete the last node from the linked list

Write a while loop to move current until it reaches the second last node (where current.next.next is None). Then set current.next to None to remove the last node.

DSA Python

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

node1 = Node(10)
node2 = Node(20)
node3 = Node(30)

node1.next = node2
node2.next = node3

head = node1

current = head

# Write a while loop to find second last node and delete last node
# Your code here

Hint

Keep moving current until the next node's next is None. Then remove the last node by setting current.next to None.

4

Print the linked list after deleting the last node

Create a variable called current and set it to head. Use a while loop to print each node's data followed by ->. Stop when current is None. After the loop, print null.

DSA Python

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

node1 = Node(10)
node2 = Node(20)
node3 = Node(30)

node1.next = node2
node2.next = node3

head = node1

current = head

while current.next.next is not None:
    current = current.next

current.next = None

# Print the linked list nodes followed by '->' and end with 'null'
# Your code here

Hint

Use a loop to print each node's data followed by '->'. After the loop, print 'null' to show the end.