Push Using Linked List Node in DSA Python - Build from Scratch

Push Using Linked List Node

📖 Scenario: You are building a simple stack using a linked list. A stack is like a pile of books where you add new books on top. Each book is a node that points to the book below it.

🎯 Goal: Create a linked list node class and use it to add (push) new nodes to the top of the stack. Then print the stack from top to bottom.

📋 What You'll Learn

Create a Node class with data and next attributes

Create a variable top to represent the top of the stack

Write code to push a new node with data 10 onto the stack

Write code to push a new node with data 20 onto the stack

Print the stack from top to bottom showing node data separated by ' -> ' and ending with 'null'

💡 Why This Matters

🌍 Real World

Stacks are used in undo features, expression evaluation, and backtracking algorithms.

💼 Career

Understanding linked lists and stack operations is essential for software development and technical interviews.

1

Create the Node class and initialize the stack top

Create a class called Node with an __init__ method that takes data and sets self.data to data and self.next to None. Then create a variable called top and set it to None to represent an empty stack.

DSA Python

# Define the Node class and initialize top
# Your code here

Hint

Think of Node as a box holding data and a pointer to the next box. The top starts empty because the stack is empty.

2

Push the first node with data 10 onto the stack

Create a new Node with data 10 and assign it to a variable called new_node. Then set new_node.next to top. Finally, update top to point to new_node.

DSA Python

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

top = None

# Push node with data 10
# Your code here

Hint

Remember, pushing means putting the new node on top and linking it to the old top.

3

Push the second node with data 20 onto the stack

Create a new Node with data 20 and assign it to new_node. Set new_node.next to top. Update top to new_node.

DSA Python

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

top = None

new_node = Node(10)
new_node.next = top
top = new_node

# Push node with data 20
# Your code here

Hint

Push the new node on top just like before, linking it to the current top.

4

Print the stack from top to bottom

Create a variable called current and set it to top. Use a while loop to traverse the linked list. In each loop, print current.data followed by -> without a newline. Move current to current.next. After the loop, print null.

DSA Python

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

top = None

new_node = Node(10)
new_node.next = top
top = new_node

new_node = Node(20)
new_node.next = top
top = new_node

# Print the stack
# Your code here

Hint

Traverse from top to bottom, printing each node's data followed by ' -> ', then print 'null' at the end.