# What Is Stack Data Structure Algorithm?

//

Heather Bennett

What Is Stack Data Structure Algorithm?

A stack is a fundamental data structure in computer science that follows the Last-In-First-Out (LIFO) principle. It is an abstract data type that represents a collection of elements, where the addition and removal of items can only be done from one end, known as the top.

## Stack Operations

There are several basic operations that can be performed on a stack:

• Push: This operation adds an element to the top of the stack.
• Pop: This operation removes and returns the topmost element from the stack.
• Peek or Top: This operation returns the topmost element without removing it from the stack.
• isEmpty: This operation checks if the stack is empty or not.

## The Stack Implementation

Stacks can be implemented using different data structures such as arrays and linked lists. Let’s look at an example implementation using an array.

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

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

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

peek() {
if (this.isEmpty()) {
return "No elements in stack";
}
return this.items[this.length - 1];
}

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

const stack = new Stack();
stack.push(10);
stack.push(20);
stack.push(30);

console.log(stack.pop()); // Output: 30
console.peek()); // Output: 20
console.isEmpty()); // Output: false
</script>```
```

In the above code snippet, we define a Stack class with the necessary methods for stack operations. The push method adds an element to the top of the stack, while the pop method removes and returns the topmost element.

The peek method returns the top element without removing it, and isEmpty checks if the stack is empty.

## Applications of Stack Data Structure

Stacks have various applications in computer science and programming. Some common examples include:

• Expression Evaluation: Stacks are often used to evaluate mathematical expressions, such as infix, postfix, and prefix.
• Function Call Stack: Stacks are used to manage function calls in programming languages.
• Undo/Redo Functionality: Stacks can be used to implement undo and redo functionality in text editors or graphic software.
• Balanced Parentheses: Stacks can help determine whether a given expression has balanced parentheses or not.

### In Conclusion

In summary, a stack is a data structure that follows the Last-In-First-Out (LIFO) principle. It allows adding and removing elements from one end only – the top.

Stacks find applications in various areas of computer science and programming due to their simplicity and efficiency. Understanding stack algorithms is essential for any programmer to effectively solve problems and optimize their code.