The ultimate guide to recursion interviews. Developed by FAANG engineers, practice with real-world C++ problems, interactive code playgrounds, and get interview-ready in just a few hours.

If you’ve ever struggled with solving coding problems using recursion, or if you’ve just got an interview coming up and want to brush up on your knowledge, you’ll definitely find this course helpful.
 
You’ll start with the basics of what recursion is and why it’s important before diving into what it looks like in practice. You’ll see how recursion can help you solve a variety of different math, string, and data structure problems, using interactive code playgrounds you can execute directly in your browser. You’ll have access to detailed explanations and visualizations for each problem to help you along the way.  
 
By the time you’re done, you’ll be able to use what you’ve learned to solve complex real-world problems, and even advance more easily through your interviews at top tech companies.

Recursion for Coding Interviews in C++

# What is a prime number?
A **prime number** is a number greater than 1, that has only two divisors: 1 and the number itself. The first few prime numbers are:

 $2, 3, 5, 7, 11, 13, 17, 19, 23, 29, .....$ 

**Composite** numbers are numbers that are not prime, that is, have divisors other than zero and itself

$4, 6, 8, 9, 10, 12, 14, 15, 16, 18.......$

>The numbers $1$ and $0$ are neither prime nor composite. 

All the numbers are either prime or composite, except for $0$ and $1$.

# Problem Statement
Write a recursive function, named `isPrime()` that checks if a number is prime or not.

## Instructions
1. The function should take two integers as input.
2. The function should return boolean $-$ return $1$  if *true* and the number is prime. Should return $0$ if *false* and the number is not prime.
3. The function should be recursive.  

**Sample Input:** 7

**Sample Output:** 1

**Sample Input:** 9

**Sample Output:** 0

Good luck!

> **Note:** Some test cases will pass by default and you need to pass all for the solution to be considered correct.

In this lesson, the user will check if a number is prime or not using recursion.

Recursion Fundamentals

Recursion with Numbers

Recursion With Strings

Recursion With Arrays

Recursion with Data Structures

Challenge 2: Check for Prime Number

What is a prime number?