Delete Node by Value in DSA Python - Build from Scratch

Delete Node by Value in a Singly Linked List

📖 Scenario: You are managing a list of tasks in a to-do app. Each task is stored as a node in a singly linked list. Sometimes, you need to remove a task by its name when it is completed or no longer needed.

🎯 Goal: Build a program that creates a singly linked list of tasks, sets the task name to delete, deletes the node with that task name from the list, and prints the updated list.

📋 What You'll Learn

Create a singly linked list with exact tasks: 'Laundry', 'Grocery', 'Homework', 'Exercise', 'Call Mom'

Create a variable called task_to_delete with the value 'Homework'

Write a function delete_node_by_value(head, value) that deletes the first node with the given value

Print the linked list after deletion in the format: Task1 -> Task2 -> ... -> null

💡 Why This Matters

🌍 Real World

Linked lists are used in many apps to manage ordered data like tasks, playlists, or history where items can be added or removed dynamically.

💼 Career

Understanding linked list operations like deletion is important for software development roles that involve data structure manipulation and memory management.

1

Create the singly linked list with tasks

Create a class called Node with attributes data and next. Then create nodes for tasks 'Laundry', 'Grocery', 'Homework', 'Exercise', and 'Call Mom' linked in that order. Assign the head of the list to a variable called head.

DSA Python

# Define Node class and create linked list nodes for tasks
# Your code here

Hint

Start by defining the Node class with data and next. Then link the nodes in order.

2

Set the task to delete

Create a variable called task_to_delete and set it to the string 'Homework'.

DSA Python

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

head = Node('Laundry')
head.next = Node('Grocery')
head.next.next = Node('Homework')
head.next.next.next = Node('Exercise')
head.next.next.next.next = Node('Call Mom')

# Create variable task_to_delete with value 'Homework'
# Your code here

Hint

Just assign the string 'Homework' to the variable task_to_delete.

3

Write the function to delete a node by value

Write a function called delete_node_by_value(head, value) that deletes the first node in the linked list whose data matches value. The function should return the new head of the list. Handle the case where the node to delete is the head.

DSA Python

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

head = Node('Laundry')
head.next = Node('Grocery')
head.next.next = Node('Homework')
head.next.next.next = Node('Exercise')
head.next.next.next.next = Node('Call Mom')

task_to_delete = 'Homework'

def delete_node_by_value(head, value):
    # Your code here

Hint

Check if the head node has the value. If yes, return head.next. Otherwise, loop through nodes to find and remove the matching node.

4

Delete the node and print the updated list

Call delete_node_by_value(head, task_to_delete) and assign the result back to head. Then print the linked list nodes' data separated by ' -> ' and ending with 'null'.

DSA Python

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

head = Node('Laundry')
head.next = Node('Grocery')
head.next.next = Node('Homework')
head.next.next.next = Node('Exercise')
head.next.next.next.next = Node('Call Mom')

task_to_delete = 'Homework'

def delete_node_by_value(head, value):
    if head is None:
        return head
    if head.data == value:
        return head.next
    current = head
    while current.next is not None:
        if current.next.data == value:
            current.next = current.next.next
            return head
        current = current.next
    return head

head = delete_node_by_value(head, task_to_delete)

# Print the linked list
# Your code here

Hint

Call the delete function and then loop through the list to print each task followed by ' -> ', ending with 'null'.