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 computes the average of all the numbers in an array.

If we have $n$ numbers where each number is denoted by $a_i$ $(where \: i = 0, 1, 2, ..., n-1)$, the average is the $sum$ of the numbers divided by $n$ or;
$$
{\displaystyle average={\frac {1}{n}}\sum _{i=0}^{n-1}a_{i}={\frac {a_{0}+a_{1}+a_{2}+\cdots +a_{n-1}}{n}}} 
$$

> Try solving this problem recursively.

### Input
1. A `testVariable` containing an array of numbers.
2. The `currentIndex` of the array.

### Output
Average of the numbers in the input array.

### Sample Input
```python
testVariable = [10, 2, 3, 4, 8, 0] 
currentIndex = 0
```

### Sample Output
```
4.5
```

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

def average(testVariable, currentIndex = 0) : 
	# Write your code here
	return None

def average(testVariable, currentIndex = 0) : 
	if currentIndex == len(testVariable) - 1 : 
		return testVariable[currentIndex] 
	
	if currentIndex == 0 : 
		return ((testVariable[currentIndex] + average(testVariable, currentIndex + 1)) / len(testVariable)) 
	
	return (testVariable[currentIndex] + average(testVariable, currentIndex + 1)) 

---
Let's have a look at the solution review of this problem.

# Problem Statement
Implement a function that computes the average of all the numbers in an array.

If we have $n$ numbers where each number is denoted by $a_i$ $(where \: i = 0, 1, 2, ..., n-1)$, the average is the $sum$ of the numbers divided by $n$ or;
$$
{\displaystyle average={\frac {1}{n}}\sum _{i=0}^{n-1}a_{i}={\frac {a_{0}+a_{1}+a_{2}+\cdots +a_{n-1}}{n}}} 
$$

> Try solving this problem recursively.

## Input
1. A `testVariable` containing an array of numbers.
2. The `currentIndex` of the array.

## Output
Average of the numbers in the input array.

## Sample Input
```python
testVariable = [10, 2, 3, 4, 8, 0] 
currentIndex = 0
```

## Sample Output
```
4.5
```

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

Given an array of numbers, compute the average of all the numbers recursively.

Recursion Fundamentals

Iteration Vs. Recursion

Recursion with Numbers

Recursion with Strings

Recursion with Arrays

Recursion with Data Structures

Conclusion

Challenge 1: Average of Numbers

Problem Statement

Input

Output

Sample Input

Sample Output

Try it Yourself