Stack Implementation Using Linked List in DSA Python - Build from Scratch

Stack Implementation Using Linked List

📖 Scenario: You are building a simple stack data structure using a linked list. A stack works like a stack of plates: you add plates on top and remove plates from the top only.This stack will help manage tasks in a to-do list app where the most recent task is handled first.

🎯 Goal: Create a stack using a linked list with push and pop operations, then display the stack content.

📋 What You'll Learn

Create a Node class with data and next attributes

Create a Stack class with top attribute initialized to None

Implement push method to add elements to the stack

Implement pop method to remove elements from the stack

Print the stack elements from top to bottom

💡 Why This Matters

🌍 Real World

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

💼 Career

Understanding stack implementation helps in coding interviews and building efficient algorithms.

1

Create Node and Stack classes

Create a class called Node with an __init__ method that takes data and sets self.data = data and self.next = None. Then create a class called Stack with an __init__ method that sets self.top = None.

DSA Python

# Your code here

Hint

Think of Node as a box holding data and a link to the next box. Stack keeps track of the top box.

2

Add push method to Stack

Inside the Stack class, create a method called push that takes self and data. Create a new Node with data. Set the new node's next to self.top. Then update self.top to the new node.

DSA Python

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

class Stack:
    def __init__(self):
        self.top = None

    # Add push method here
    # Your code here

Hint

Push means adding a new node on top. Link the new node to the old top, then update top.

3

Add pop method to Stack

Inside the Stack class, create a method called pop that takes self. If self.top is None, return None. Otherwise, save self.top.data in a variable, update self.top to self.top.next, and return the saved data.

DSA Python

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

class Stack:
    def __init__(self):
        self.top = None

    def push(self, data):
        new_node = Node(data)
        new_node.next = self.top
        self.top = new_node

    # Add pop method here
    # Your code here

Hint

Pop means removing the top node and returning its data. If stack is empty, return None.

4

Print stack elements from top to bottom

Create a Stack object called stack. Use stack.push to add 10, 20, and 30 in that order. Then create a variable current and set it to stack.top. Use a while loop to print current.data followed by ' -> ' until current is None. After the loop, print None.

DSA Python

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

class Stack:
    def __init__(self):
        self.top = None

    def push(self, data):
        new_node = Node(data)
        new_node.next = self.top
        self.top = new_node

    def pop(self):
        if self.top is None:
            return None
        popped_data = self.top.data
        self.top = self.top.next
        return popped_data

# Create stack and push elements
# Your code here

Hint

Remember, the last pushed item is on top. Print from top to bottom with arrows.