Finally! A proven strategy for quickly solving any recursive problem...

...even if you suck at interviewing.

You know what I friggin’ hate?

“To understand recursion, one must understand recursion.”

And I’m not alone either. This was one of the survey responses when I asked my readers about recursion:

Whenever I see someone make this “joke”, they get a dry, sarcastic laugh from me.

Ha. Ha.

Seriously, if I had a bitcoin for every time…

But I digress. Here’s the thing about statements like this: They display a lack of true understanding.

It’s the same as saying “recursion is just breaking down a problem into subproblems” or “recursion is just a function that calls itself”.

Sure. Those are both valid statements, but how do they help you use recursion? How the hell do you break down a permutation problem to begin with?

Imagine this…

You’ve been studying for weeks for your upcoming interview at Facebook. It’s been years since you’ve had to do any data structures and algorithms, but you went back to your sophomore year class notes to really make sure that you were covering your bases.

You went over graphs and trees – gotta remember how to implement Dijkstra’s algorithm.

You studied system design – you could design a messaging app or TinyURL in your sleep.

You covered recursion – Fibonacci? No problem. Factorial? Check!

The day of reckoning is finally here. Of course you’re nervous, why wouldn’t you be? But at the same time, you know you’ve done everything you can to prepare. You walk into your first interview…

And that’s where the problems start.

“Write a function to find all permutations of a list.”

I guess we could use a for loop to loop over each choice for each item in our list…

But then we would need to have n nested for loops…

I think I remember something about doing this recursively…

Are we supposed to swap items somehow? But if we swap them then how the hell does that actually work?

And what is our base case anyway? And how are we breaking down the problem?

You fumble your way through the problem. Ultimately, you’re able to piece together a solution, and about 45 minutes later, you wrap up the question on the whiteboard, have a friendly chat with you interviewer, and go on your merry way.

The interview definitely left you a little spooked – that was harder than you expected, especially given how much you studied – but you continue on to do well on all the rest of your interviews.

Leaving Facebook campus at the end of the day, you feel good. Sure everything didn’t go perfectly, but it went better than you expected and you have confidence that you’re going to get an offer.

Two days later, you get a cold, formulaic rejection email.

You know why?

Remember that permutation problem that took you 45 minutes?

Well it turns out, they were expecting more. What you found to be a challenging problem was actually part 1 of what should have been a 3 part interview. When you struggled on the EASY part, they skipped the rest.

So what happened? Why did you struggle so much on this simple problem?

Simply put, no one ever taught you how to really do recursion. In school, you learn the same basic concepts.

→ Break down the problem into subproblems.

→ Write a function that calls itself.

→ Find the base case and recursive step.

→ “Look how easy it is to do Fibonacci and Factorial”.

But you’re missing the most important part! No one ever teaches you how to apply what you’re learning.

Instead of coming into the interview with a clear, step-by-step strategy, you stare at the problem and fumble around until you kinda sorta come up with a solution.

All you’re taught is how to regurgitate solutions to simple recursive problems.

But guess what? Those aren’t the questions interviewers ask.

Interviewers don’t care if you can repeat solutions that you’ve seen before. They care whether you can come up with new solutions. They care about your problem solving skills.

And unfortunately no one teaches you to think about recursion.

Recursion is one of those topics where you are taught the bare minimum and then expected to go out on your own and figure it out.

That would be like you asking for directions to drive to the grocery store 3 miles away and me vaguely pointing and saying “that way”. You’ll get there eventually. After stopping to ask for directions. And doubling back a few times. And getting hopelessly lost.

What if instead, I took the time to actually draw you a map. I could show you which way to turn at which intersection so that you can get to the store by the fastest route? I’ve been there before, so I know how to get there.

Now I know for driving directions, this is obvious. We’ve all used Google Maps.

But I’m here to show you the “Google Maps” of recursion.

In fact, over the last 3 months, I’ve gone through literally dozens of the most common recursion problems to find the patterns that tie each problem together. I’ve spent months identifying common threads so that I can really understand how to approach any recursive problem and successfully find a solution.

I’ve worked with an intrepid group of student explorers to develop a roadmap that you can follow so that recursion is no longer something to fear.

Multiple students found that by using this roadmap, they began to actively enjoy using recursion and started seeking out places that they could use it in their interviews.

Recursion is now something I can comfortably say I’ll be using a lot more when I now go back into taking on more problems on HackerRank.

– Peter K.

Imagine if you had a clear picture of how to solve any recursive problem. When you go into your interview with any company, you can have confidence walking in and holding your head high, knowing for a fact that you’re going to come out having blown them away.

Imagine that you could sleep comfortably at night knowing that no interview problem is too challenging for you to solve.

Imagine coming home from your interviews to your phone ringing off the hook with recruiters tripping over each other to give you a job offer.

The best candidates have their pick of the good jobs

Imagine recruiters fighting over you, giving you the chance to negotiate tens of thousands of $$$.

Imagine walking down Hacker Way for the first day of your shiny new job!

All of this is possible… but not unless you become a master of recursion.

Now, it is certainly possible to master recursion on your own.

As a matter of fact, here’s what I did:

Get a Computer Science degree (19 required courses, ~2000 hours)
Study a functional programming language (~100 hours)
Study and interview for countless jobs (~100 hours)

You’re more than welcome to follow in my footsteps.

You could google around and find what articles you can on recursion. Then you can filter through the mess of fibonacci and factorial crap to possibly find something useful. If you go through the articles, you’ll probably be able to piece everything together – if you dig through the hundreds of pages it takes to get there.

You could go on Leetcode and memorize the solution to every recursive problem. That might work, in the off chance that you get asked one of those exact questions. Or after the 40th problem, you may start to recognize some patterns. But do you really want to risk losing a job because you were too lazy to go more than surface deep?

You could go to the source and study the mathematical theory. Once you understand induction and theoretical proofs, you may be able to use that to develop algorithms to solve some of these recursive problems. That’s some crazy hard, Ph.D-level crap though.

However, these are all incredibly time consuming solutions. Do you really have time for this? Your interview is coming up soon. You’re working a fulltime job. The last thing you need to do is redo all this work that I’ve already done for you.

Rather than trying to figure everything out on your own, let me share my tried and true strategies with you!

Introducing...

Coding Interview Mastery: Recursion

What if recursion was as easy for you as it is for everyone else? Everyone else can get whatever job offer they want and you’re stuck here muddling through function calls.

It’s basically hieroglyphics…

I used to think there was a natural pecking order. That some people were just smarter than others…

…but as I began to dig deep into recursion, I realized I was wrong.

Going through problem after problem, patterns started to emerge. The dots started to connect. And that’s when I realized… these people aren’t actually any smarter than me.

They didn’t have any special skills. They weren’t uniquely gifted. They just literally knew something that I didn’t.

They had the cheat codes.

And that’s what this course is. It’s the hacks that no one shows you. The ones that everyone else either doesn’t know or don’t realize they’re using…

Here are just a few of the things you’ll learn in this course:

The 6 “Cheat Codes” to Unlock Any Recursive Problem

The deeper I dug into the recursion, the more I began to see what felt like secret patterns that unlocked the solutions to each problem.

It always seemed like every problem was completely different. Every interview question was a fresh hell…

But then I realized that there were 6 – only 6 – patterns that I needed to know. Armed with these, I had solved 70% of any problem before I even started…

Imagine if you only had to do 30% of the work of everyone else! It’s almost unfair.

X-Ray Any Recursive Code to Expose Its Hidden Meaning

I kept getting stuck. I wanted to learn how a problem worked, but I would look at the code and it was so over my head. That’s when I found this little-known strategy for dissecting any recursive code and revealing it’s true meaning…

With this technique, we can look under the hood and see what is really going on in any recursive code. We can learn from the masters… and become masters ourselves.

Compute the Time Complexity in 30 Seconds or Less

I used to try to find the time complexity of recursive and the best I could come up with was O(WTF).

As I discovered the patterns of recursive problems, I also found one clever little trick that completely changed everything. With this trick, you don’t have to compute the time complexity at all 99% of the time.

This formula gives you the time complexity for any recursive problem in seconds flat.

Here's how the course works:

Coding Interview Mastery: Recursion isn’t just a collection of random recursive problems. It’s not hours of boring lectures about everything known to man about recursion.

You don’t have time for that.

I don’t have time for that.

That’s why I’ve condensed exactly what you need to know into this 7 module intensive training course. No fluff. Just exactly what you need so that you get get back to interviewing.

In each module, we break down one of the core recursive patterns and go deep. You will learn the pattern and then see multiple examples of exactly how to apply it. I’ll show you exactly how to use these cheat codes to unlock any recursive problem your interviewer can throw at you.

You’ll also have homework. This will drill the concepts into your head so that you can’t possibly forget them. Each question is carefully chosen to reinforce a specific point. Again, no fluff.

“[My favorite aspect of the course was] definitely the exercises, the homework. [They] started from the easiest, but still within the same lesson there was, I mean that the last homework exercise was usually the most difficult one. And I think it was beyond the comfortable level for me, so that I really had to challenge myself usually with the last one… I think it was good that it was a challenging part of that course, so really push myself.”

– Jaro K.

And because I know that we sometimes get busy, I’m giving you lifetime access to this course.

The Course Includes

Module 1 — Recursion Fundamentals

In Module 1, you will learn all the foundations of recursion that you will need and we’ll make sure that everybody is starting on the same page. This isn’t a beginner course, but we’ll quickly review all the basics.