What Type of Data Structure Is Stack?

A stack is a fundamental data structure in computer science. It follows the principle of Last-In-First-Out (LIFO), which means that the last element added to the stack will be the first one to be removed. In this article, we will explore what a stack is, how it works, and some common use cases for this data structure.

Definition

A stack is a linear data structure that stores a collection of elements. It has two main operations: push and pop. The push operation adds an element to the top of the stack, while the pop operation removes and returns the topmost element.

Unlike arrays or linked lists, stacks have restricted access points. They can only be accessed from one end called the top. This makes stacks efficient for certain types of operations, such as managing function calls in programming languages or handling undo/redo functionality in text editors.

Implementation

A stack can be implemented using various programming languages. One common approach is to use an array or a linked list. Let’s see how we can implement a stack using an array:

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

  push(element) {
    this.items.push(element);
  }

  pop() {
    if (this.isEmpty()) {
      return "Underflow";
    }
    return this.pop();
  }

  peek() {
    return this.items[this.length - 1];
  }

  isEmpty() {
    return this.length === 0;
  }

  size() {
    return this.length;
  }
}

const myStack = new Stack();
myStack.push(10);
myStack.push(20);
myStack.push(30);
console.log(myStack.pop()); // Output: 30
console.peek()); // Output: 20

In the above example, we create a Stack class with methods like push, pop, peek, isEmpty, and size. The push method adds an element to the top of the stack, the pop method removes and returns the topmost element, and the peek method returns the topmost element without removing it.

Common Use Cases

Stacks have various practical applications in computer science. Some common use cases include:

• Function call management: Stacks are used to manage function calls in programming languages. When a function is called, its execution context is pushed onto the stack.

  Once the function finishes executing, its context is popped from the stack.

• Expression evaluation: Stacks are used to evaluate arithmetic expressions. Infix expressions can be converted to postfix notation using stacks for efficient evaluation.
• Undo/redo functionality: Stacks are employed in text editors and other applications to implement undo/redo functionality. Each state change is stored as a stack entry, allowing users to undo or redo their actions.
• Backtracking algorithms: Stacks are utilized in backtracking algorithms like depth-first search (DFS) for maintaining visited nodes or tracking a path.

In conclusion,

A stack is a versatile data structure that follows the Last-In-First-Out principle. It can be implemented using arrays or linked lists and has operations like push, pop, peek, isEmpty, and size. Stacks find applications in function call management, expression evaluation, undo/redo functionality, and backtracking algorithms.

If you’re interested in learning more about data structures, be sure to check out our other tutorials on arrays, linked lists, queues, and more!