The ultimate guide to recursion interviews with strategies developed by FAANG engineers. Practice with real-world interview questions, detailed explanations, and visualizations to prep faster.

If you’ve got an interview coming up and want to brush up on your knowledge, or if you’ve ever struggled with solving coding problems using recursion, you'll 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 by using interactive code playgrounds that 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 Java

# What is GCD?

The GCD of two integers is the largest integer that can fully divide both numbers, without a remainder.

## How to find GCD?
**What is the greatest common divisor of 54 and 36?**

The number $36$ can be expressed as a product of two integers in several different ways:

$$ 36\times 1=18\times 2= 12\times 3 = 9\times 4$$

Thus the divisors for $36$ are $1, 2, 3, 4, 6, 9, 12,  18, 36$.

The number $54$ can be expressed as a product of two integers in several different ways:

$$ 54\times 1=27\times 2= 18\times 3=9\times 6 $$

Thus the divisors for $54$ are $1, 2, 3, 6, 9, 18, 27$.

Common divisors are $1, 2, 3, 6, 9$ and $18$.
The greatest common divisor or GCD for $36$ and $54$ is $18$.

In this lesson, we will find the greatest common divisor (GCD) using recursion. 

Challenge 1: Find the Greatest Common Divisor

In this lesson, we will find the greatest common divisor (GCD) using recursion.

Fundamentals of Recursion

Iteration to Recursion

Recursion with Numbers

Recursion with Strings

Recursion with Arrays

Recursion with Data Structures

Challenge 1: Find the Greatest Common Divisor

What is GCD?

How to find GCD?