The ultimate recursion guide! Master basics, solve real-world problems, and get interview-ready in hours with FAANG engineers’ proven strategies.

If you’ve ever struggled with solving coding problems using recursion, or if you need to brush up your recursion skills for an interview, this course is for you! We will start with the basics of recursion before we practice solving actual coding problems. 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 of recursion to solve complex, real-world problems. We hope that this course will help you ace all the recursion related questions during interviews at top tech companies!

Recursion for Coding Interviews in Python

## Problem Statement
Implement a function that sorts the input array `testVariable` **in-place**.

**In-place** means that no **extra** array or any other data structure is used in the algorithm. Such algorithms produce an output in the **same memory/space** that contains the data by transforming the input `in-place`. However, a **constant** extra space can be used in the form of simple variables.

> Remember to solve this problem recursively.

### Input
1. An array `testVariable` containing numbers.
2. The length of the array

### Output
No output. Our task is to sort the input array.

### Sample Input
```python
testVariable = [5, 4, 2, 3, 1]
length = 5
```

### Sample Output
```python
# No explicit output. 
# However the state of array testVariable is [1, 2, 3, 4, 5]
```

### Try it Yourself
Try this challenge yourself before examining the solution. Good luck!

# Problem Statement
Implement a function that sorts the input array `testVariable` **in-place**.

**In-place** means that no **extra** array or any other data structure is used in the algorithm. Such algorithms produce an output in the **same memory/space** that contains the data by transforming the input `in-place`. However, a **constant** extra space can be used in the form of simple variables.

> Remember to solve this problem recursively.

## Input
1. An array `testVariable` containing numbers.
2. The length of the array

## Output
No output. Our task is to sort the input array.

## Sample Input
```python
testVariable = [5, 4, 2, 3, 1]
length = 5
```

## Sample Output
```python
# No explicit output. 
# However the state of array testVariable is [1, 2, 3, 4, 5]
```

## Try it Yourself
Try this challenge yourself before examining the solution. Good luck!

Given an array of numbers, sort it in ascending order.

Recursion Fundamentals

Iteration Vs. Recursion

Recursion with Numbers

Recursion with Strings

Recursion with Arrays

Recursion with Data Structures

Conclusion

Challenge 3: Sort an Array

Problem Statement

Input

Output

Sample Input

Sample Output

Try it Yourself