What Is Data Structure Stacks?

//

Larry Thompson

Data structures are essential concepts in computer science that allow us to organize and manipulate data efficiently. One such data structure is the stack. In this article, we will explore what a stack is, how it works, and its various operations.

What is a Stack?
A stack is a linear data structure that follows the Last-In-First-Out (LIFO) principle. It can be visualized as a stack of books where you can only access the topmost book. This means that the last element added to the stack will be the first one to be removed.

Stack Operations:
A stack supports three primary operations:

  • Push: Adds an element to the top of the stack.
  • Pop: Removes and returns the topmost element from the stack.
  • Peek: Returns the value of the topmost element without removing it.

Implementation of Stack

There are several ways to implement a stack, but one common approach is using an array or a linked list.

Array-based Implementation:
In this approach, we use an array to store elements and keep track of the topmost element’s index. Let’s take a look at some code snippets for implementing basic operations on a stack using an array:

“`html

<script>
class Stack {
  constructor() {
    this.items = [];
    this.top = -1;
  }

  push(element) {
    this.top++;
    this.items[this.top] = element;
  }

  pop() {
    if (this.isEmpty()) return "Stack Underflow";
    const removedElement = this.top];
    this.top--;
    return removedElement;
  }

  peek() {
    if (this.isEmpty()) return "Stack is empty";
    return this.top];
  }

  isEmpty() {
    return this.top === -1;
  }
}

// Create a new stack
const stack = new Stack();

// Push elements onto the stack
stack.push(10);
stack.push(20);
stack.push(30);

// Print the topmost element
console.log(stack.peek()); // Output: 30

// Pop an element from the stack
console.pop()); // Output: 30

</script>

“`

Linked List-based Implementation:
Alternatively, we can use a linked list to implement a stack. Each node of the linked list will contain an element and a reference to the next node.

“`html

<script>
class Node {
constructor(element) {
this.element = element;
this.next = null;
}
}

class Stack {
constructor() {
this.top = null;
}

push(element) {
const newNode = new Node(element);
newNode.next = this.top;
this.top = newNode;
}

pop() {
if (this.top.element;
this.top = this.next;
return removedElement;
}

peek() {
if (this.element;
}

isEmpty() {
return !this.top;
}
}

Applications of Stacks

Stacks find applications in various domains, including:

  • Expression evaluation and syntax parsing.
  • Function call stack in programming languages.
  • Undo/Redo functionality in text editors.
  • Backtracking algorithms.

In conclusion, a stack is a fundamental data structure that follows the Last-In-First-Out principle. It can be implemented using arrays or linked lists, allowing for efficient insertion and removal of elements. Understanding stacks and their operations is crucial for building efficient algorithms and solving complex problems.