Introduction: Stack is an important data structure which has uses everywhere. Here are some of the real life uses and applications of the stack data structures.

Stack is important data structures which have uses in many core concepts of programming.

## What is a Stack?

Stack is an abstract data type and data structure which is based on LIFO (last in first out). It means the last element that will go inside the stack comes out first.

Stack allows push and pop operations. Push operation adds element on the top of the stack and Pop operation removes the topmost element from the stack.

## Stack Applications and Real-life Uses

### Expression Evaluation

Stack data structure is used in evaluation of infix, prefix and postfix notation. The stack data structure also has applications in converting infix, prefix and postfix to each other.

### Backtracking

Backtracking is an algorithm technique that tries to find each and every possible combination of the technique and find the solution to a problem.

Suppose we are coding a chess-playing algorithm and at a certain point, the algorithm finds that a set of steps fails to win. In this situation, the algorithm will reverse back to the safe state and try another possible set of steps.

This "reverse back" (undo) is powered by the stack data structure which keeps track of the steps for rollback if anything goes wrong.

### Parenthesis Balance Checking

It is a common question during interviews to write a program to check if the parenthesis is balanced or not.

We use the stack data structure to check unbalanced parenthesis by pushing open brackets into the stack and pop out after a closing bracket. If nothing lasts at the end then all parenthesis are matched.

### Track nested function calls

Nested function calls are common things but complicated ones. The stack data structure is used to track the order in which the functions were invoked and return data in the same manner.

### Undo Button

As explained in backtracking example, the stack data structure has many applications in the Undo functionality of many applications. It keeps track on the work and recovers the previous stage as saved in the stack.

### Recursion

Recursion is a beautiful but dangerous (infinity) part of programming. Stack data structure is used to keep track of recursive calls and return data in a particular order.

## When you should use stack?

You can use stack when you want to get them in the reverse order as you put them.

Example to reverse a string, we want to reverse "coder" then we will push "c", "o", "d", "e", "r" into the stack and pop operation will take them out as "r", "e", "d", "o", "c". Now we can combine them and we get the reverse of the string.

## Summary

Here is a summary of all the applications of stack data structures.

- Expression evaluation
- Backtracking
- Balanced parenthesis check
- Track nested functions call
- Undo functionality
- Recursion