# Which Data Structure Follows Last in the First Out Rule?

//

Larry Thompson

Which Data Structure Follows Last in the First Out Rule?

When it comes to data structures, there are various types that serve different purposes. One important characteristic of a data structure is its behavior when it comes to accessing and manipulating data.

In some cases, we require a specific order for how elements are processed. One such order is Last in First Out (LIFO), where the last element that is inserted into the structure is the first one to be removed.

## Stack – The LIFO Data Structure

One commonly used data structure that follows the LIFO rule is the stack. A stack is like a pile of objects where you can only access or remove the topmost element.

It operates on two main operations: push, which adds an element to the top of the stack, and pop, which removes the topmost element from the stack.

To further illustrate how a stack works, let’s consider an example using a physical stack of books. Imagine you have a pile of books on your desk, with each book representing an element in the stack.

When you add a new book, you place it on top of the existing books. Similarly, when you remove a book from your stack, you always take it from the top.

### Stack Operations

In addition to push and pop operations, stacks also support other useful operations:

• Peek: Retrieves but does not remove the topmost element of the stack.
• isEmpty: Checks if the stack is empty.
• size: Returns the number of elements in the stack.

These operations make stacks versatile and useful in a wide range of applications. For example, they are often used in algorithms that require backtracking, as they allow you to easily undo or revert previous actions.

## Implementation of a Stack

Stacks can be implemented using various programming languages. Here is a simple implementation using JavaScript:

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

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

pop() {
if (this.isEmpty()) {
return "Stack is empty";
}
return this.pop();
}

peek() {
if (this.stack[this.length - 1];
}

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

size() {
return this.length;
}
}

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

// Add elements to the stack
myStack.push(10);
myStack.push(20);
myStack.push(30);

// Remove the topmost element from the stack
console.log(myStack.pop()); // Output: 30

// Check the topmost element without removing it
console.peek()); // Output: 20

// Check if the stack is empty
console.isEmpty()); // Output: false

// Get the size of the stack
console.size()); // Output: 2
```
```

In this example, we define a `Stack` class with its respective methods. The `push()` method adds an element to the top of the stack, while `pop()` removes and returns the topmost element.

The `peek()` method allows us to check the topmost element without removing it. The `isEmpty()` method checks if the stack is empty, and the `size()` method returns the number of elements in the stack.

## Conclusion

In summary, when you need a data structure that follows the Last in First Out (LIFO) rule, a stack is your go-to choice. Stacks are widely used in various applications and can be implemented using different programming languages.

Understanding how stacks work and their operations will empower you to efficiently solve problems that require LIFO behavior.

Now that you have a solid understanding of stacks, explore further and experiment with different use cases to enhance your programming skills!