If you’ve ever struggled with solving problems using recursion, or if you have to brush up your skills for an interview, this course is for you.

We'll start with the basics of what recursion is and why it’s important before diving into practicing solving actual questions. You’ll have access to detailed explanations and visualizations for each problem to help you along the way. 

By the time you have completed this course, you’ll be able to use all the concepts to solve complex real-world problems. We hope that through practicing recursion, you will be able to ace all recursion related questions in interviews at top tech companies.

Solving Problems with Recursion in Python

## Problem Statement
Implement a function that takes a stack `testVariable` and reverses it. **Make sure you do not create any other extra stack or data structure.**

> Helper functions are provided in the file `stack.py`. Have a look at it before implementing your solution.

### Input
A variable `testVariable` that contains a stack.

### Output
No **explicit output**. Just reverse the contents of the stack.

### Sample Input
```
8, 5, 3, 2
```




### Sample Output
No explicit output. The contents of the stack will be reversed. For the given sample input the contents of the stack will be `2, 3, 5, 8`.



### Try it Yourself
Try to attempt this challenge by yourself before moving on to the solution. Good luck!

# HELPER FUNCTION FOR CREATING AND MANIPULATING A STACK

def createStack() : # Function to create an empty stack
  stack = []
  return stack 

def isEmpty(stack) :
  return len(stack) == 0

def push(stack, item) : # push item to stack
  stack.append( item ) 

def pop(stack) : # pop item from stack

  if(isEmpty(stack)) : # display error if stack empty  
    print("Stack Underflow ")
    exit(1)

  return stack.pop() 

import stack as s
 
def reverse(testVariable) :
  # Write your code here
  return None

import stack as s
 
def insertAtBottom(stack, item) : # Creating a helper function
  if s.isEmpty(stack) :
    s.push(stack, item)

  else:
    temp = s.pop(stack)
    insertAtBottom(stack, item)
    s.push(stack, temp) 

def reverse(testVariable) :
  if not s.isEmpty(testVariable) :
    temp = s.pop(testVariable)
    reverse(testVariable)
    insertAtBottom(testVariable, temp)

---
In the next lesson, we have a solution review of this problem.

# Problem Statement
Implement a function that takes a stack `testVariable` and reverses it. **Make sure you do not create any other extra stack or data structure.**

> Helper functions are provided in the file `stack.py`. Have a look at it before implementing your solution.

## Input
A variable `testVariable` that contains a stack.

## Output
No **explicit output**. Just reverse the contents of the stack.

## Sample Input
```
8, 5, 3, 2
```




## Sample Output
No explicit output. The contents of the stack will be reversed. For the given sample input the contents of the stack will be `2, 3, 5, 8`.



## Try it Yourself
Try to attempt this challenge by yourself before moving on to the solution. Good luck!

Given a stack, reverse the contents of the stack.

Recursion Fundamentals

Iteration Vs. Recursion

Recursion with Numbers

Recursion with Strings

Recursion with Arrays

Recursion with Data Structures

Conclusion

Challenge 2: Reverse a Stack

Problem Statement

Input

Output

Sample Input

Sample Output

Try it Yourself