# What Is LIFO in Data Structure?

//

Heather Bennett

What Is LIFO in Data Structure?

In computer science, LIFO stands for Last-In-First-Out, which is a method of organizing and manipulating data. It is a fundamental principle in data structures and is widely used in various applications.

## Understanding LIFO

LIFO follows the principle of “last in, first out,” meaning that the last item added to the data structure will be the first one to be removed. This concept can be visualized as a stack of items where new elements are added on top and removed from the top.

In LIFO, elements are added and removed from only one end of the data structure, known as the top. This makes it easy to access and manipulate the most recent element without affecting other elements in the stack.

## Applications of LIFO

LIFO is used extensively in computer programming and software development due to its simplicity and efficiency. Some common applications include:

• Function call stack: When a function is called, its return address and local variables are stored on a stack. The most recent function call gets executed first, allowing for recursive function calls.
• Undo/Redo functionality: In many applications, such as text editors or graphic design software, LIFO is used to implement undo/redo operations by storing states or actions on a stack.
• Browsing history: Web browsers use LIFO to track visited URLs so that users can navigate back through previously visited pages using the “Back” button.
• Evaluation of expressions: LIFO is utilized in evaluating arithmetic expressions by using stacks to store numbers, operators, and parentheses.

## Implementing LIFO in Data Structures

There are several ways to implement LIFO in data structures, but the most common approach is by using a stack. A stack is a linear data structure that follows the LIFO principle.

In programming languages like C++, Java, or Python, stacks are often implemented using arrays or linked lists. These implementations provide methods to push (add) elements onto the stack and pop (remove) elements from the top of the stack.

### Example:

``````
// Implementation of a stack using an array
class Stack {
private:
static const int MAX_SIZE = 100;
int arr[MAX_SIZE];
int top;

public:
Stack() {
top = -1;
}

void push(int element) {
if (top >= MAX_SIZE-1) {
cout << "Stack Overflow!" << endl;
return;
}
arr[++top] = element;
}

int pop() {
if (top < 0) {
cout << "Stack Underflow!" << endl;
return -1; // Or throw an exception
}
return arr[top--];
}
};
```
```

In this example, the `push()` function adds an element to the top of the stack, while the `pop()` function removes and returns the topmost element.

## Conclusion

LIFO is a fundamental concept in data structures that allows for efficient storage and retrieval of elements. Understanding LIFO and its applications can greatly enhance your problem-solving skills and help you design more efficient algorithms.

To summarize:

• LIFO stands for Last-In-First-Out.
• It follows the principle of "last in, first out."
• Common applications include function call stacks, undo/redo functionality, browsing history, and expression evaluation.
• LIFO is typically implemented using a stack data structure.

By incorporating LIFO into your programming knowledge, you'll have a valuable tool for solving a wide range of problems efficiently.