Lecture 11 – Introduction to STACK in Data Structure (മലയാളത്തിൽ) – Data Structures

Introduction

This tutorial provides an introduction to stacks, a fundamental concept in data structures. Stacks are linear data structures that operate on a specific order, primarily known as Last In First Out (LIFO) or First In Last Out (FILO). Understanding stacks is crucial for various programming applications, such as managing function calls, undo mechanisms in software, and parsing expressions.

Step 1: Understanding Stack Basics

• Definition: A stack is a linear data structure where elements are added or removed from one end, referred to as the "top" of the stack.
• Key Characteristics:
  • LIFO Principle: The last element added to the stack is the first one to be removed.
  • Operations: The primary operations performed on a stack are:
    • Push: Adding an element to the top of the stack.
    • Pop: Removing the element from the top of the stack.
    • Peek: Viewing the top element of the stack without removing it.

Step 2: Implementing a Stack

• Choose a Programming Language: You can implement a stack in various programming languages. Here’s an example in Python:

class Stack:
    def __init__(self):
        self.items = []

    def is_empty(self):
        return len(self.items) == 0

    def push(self, item):
        self.items.append(item)

    def pop(self):
        if not self.is_empty():
            return self.items.pop()
        else:
            return "Stack is empty"

    def peek(self):
        if not self.is_empty():
            return self.items[-1]
        else:
            return "Stack is empty"

    def size(self):
        return len(self.items)

• Explanation of Code:
  • __init__: Initializes an empty stack.
  • is_empty: Checks if the stack is empty.
  • push: Adds an element to the top of the stack.
  • pop: Removes and returns the top element. Returns a message if the stack is empty.
  • peek: Returns the top element without removing it. Also checks if the stack is empty.
  • size: Returns the number of elements in the stack.

Step 3: Common Applications of Stacks

• Function Calls: Stacks keep track of function calls in programming languages.
• Undo Mechanisms: Many applications use stacks to implement "undo" functionality, where the most recent action can be reversed.
• Expression Evaluation: Stacks are used in parsing expressions and syntax checking in compilers.

Step 4: Potential Pitfalls

• Stack Overflow: Occurs when too many elements are added beyond the predetermined limit, especially in recursive functions.
• Stack Underflow: Happens when attempting to remove an element from an empty stack.

Conclusion

Stacks are essential data structures that facilitate various programming tasks through their LIFO nature. Understanding how to implement and utilize stacks can significantly enhance your programming skills. To further your knowledge, consider exploring advanced topics like stack memory management and implementing stacks with different data types.