Stack

Introduction:

In computer science, the stack is an essential data structure that plays a significant role in organizing and managing elements. Often referred to as a Last-In-First-Out (LIFO) structure, the stack allows for efficient data storage and retrieval. In this article, we will explore the stack data structure, its fundamental operations, and how it is used in various programming languages. Let’s dive in!

Understanding the Stack Data Structure:

The stack is an abstract data type that serves as a collection of elements. It follows a simple principle: the last element added is the first one to be removed. Imagine a stack of books, where the most recently placed book is the first one to be picked up. This analogy helps us grasp the concept of a stack.

Fundamental Operations of a Stack:

Push: The push operation adds an element to the top of the stack. It increases the stack’s size and places the new element as the most recently added item.

Pop: The pop operation removes the topmost element from the stack. It returns the removed element and decreases the stack’s size. Here are the code examples:

Applications of the Stack Data Structure:

The stack data structure finds numerous applications in computer science and programming. Here are a few common use cases:

Function Calls: In programming languages, the stack is used to manage function calls. Each function call is pushed onto the stack, and when a function returns, it is popped off the stack, allowing the program to resume execution from the previous point.

Expression Evaluation: The stack is widely used in evaluating arithmetic expressions. It helps in determining the order of operations and ensures that the calculations are performed correctly.

Undo/Redo Operations: In many applications, such as text editors or graphic design software, the stack is utilized to implement undo and redo operations. Each action is pushed onto the stack, allowing users to go back and forth between different states.

Links

Code Examples

C#
using System.Collections;
Stack stack = new Stack();
stack.Push("A");
stack.Push("B");
int poppedItem = stack.Pop();

JavaScript
class Stack {
    constructor() {
        this.elements = [];
    }

    push(item) {
        this.elements.push(item);
    }

    pop() {
        if (this.elements.length === 0)
            throw new Error("Stack is empty");

        return this.elements.pop();
    }
}

// Usage
const stack = new Stack();
stack.push(10);
stack.push(20);
const poppedItem = stack.pop();

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

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

    def pop(self):
        if len(self.elements) == 0:
            raise IndexError("Stack is empty")
        return self.elements.pop()

PHP
<?php
class Stack {
    private $elements = [];

    public function push($item) {
        $this->elements[] = $item;
    }

    public function pop() {
        if (empty($this->elements))
            throw new Exception("Stack is empty");

        return array_pop($this->elements);
    }
}

// Usage
$stack = new Stack();
$stack->push(10);
$stack->push(20);
$poppedItem = $stack->pop();

Conclusion