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 the modulo operation?
The modulo operation (abbreviated as **mod**) finds the remainder after the division of one number - the **dividend**, by another number - the **divisor**. 

Below is an image to revise the concept of the remainder using a basic division example: 





In the example above, we have divided 14, the dividend, by 4, the divisor. 3 is the quotient and 2 is the remainder. 

If we were to use a mod function, it would be implemented as follows:

We read this as 14 *mod* 4 is equal to 2.
  
>**Note:** If the dividend is fully divisible by the divisor, the remainder is $0$.

Below is a short quiz to test whether you have grasped the concept of mod operation or not:


In this lesson, we will learn about the modulo operation and how to implement it using recursion.

Recursion Fundamentals

Recursion with Numbers

Recursion With Strings

Recursion With Arrays

Recursion with Data Structures

Modulo Using Recursion

What is the modulo operation?