The Intuitive Guide to Data Structures and Algorithms

https://www.interviewcake.com/data-structures-and-algorithms-guide

by leeny • 9 years ago

362 62 9 years ago

gameguy4313• 9 years ago

Thanks for the post! Original author here. Happy to answer questions.

namanyayg• 9 years ago

This is something I've entered my email into after at least a year or so. Great presentation and design and I'm sure it's good content too -- I'll get to know over the coming week :)

tenaciousDaniel• 9 years ago

I really love this. Frustratingly few articles/posts/courses actually follow through on their promise to make difficult material intuitive. I'm only halfway through your Big-O post but it's already obvious that you've put a lot of care into really making it accessible.

Well done!

gameguy4313• 9 years ago

That is soooo great to hear because every time we "finish" writing a new piece we end up spending literal /months/ obsessively polishing it before taking it live.

I always worry that we're just spinning our wheels. But it's great to hear that the extra effort is showing through :)

notjackson• 9 years ago

I really liked how you've added the option to select between many programming languages in the snippets!

Did you write each of them yourself or is there a way to automate such simple code already?

gameguy4313• 9 years ago

We have a team of like a dozen and a half contractors from around the world who do the translations.

It was important to us to not just translate our Python into C++, but to have C++ that was actually good, C++-style C++. So we hired C++ experts to do all the C++ translations. And same for the other languages.

Now, none of us are C++ experts. So how did we know if the contractors we hired were any good? That's a whoooole blog post for another time.

In short: Noah (an engineer on the team) came up with this clever system where we hired a bunch of people to translate the same code sample (as a paid trial task), then we hired a bunch of people to rate those people's translations (again, as a paid trial task). Then we hired the translator who had the best ratings, and we also hired the /rater/ who was most /thorough/--they do code reviews of the translator's code.

xenihn2• 9 years ago

Happy customer since 2015. Any plans to add Go or Rust translations?

gameguy4313• 9 years ago

No specific plans yet. But notes like this are how we decide which languages to add next!

Curious: what language do you currently use on the site? And how painful is it for you to not have Go or Rust?

(Also, you're talking about having the /content/ in those languages, right? Or supporting those languages in our code editor?)

vvanders• 9 years ago

Shoutout for including the bit about constants in O(n) notation, 99% of things I see cover it gloss over it.

I've seen radix sort walk all over quicksort for common datasets many times. Knowing your dataset is at least as important as knowing the right algorithm.

gregable• 9 years ago

This is really beautiful. I love that the images are SVGs as well, makes perfect sense for these line drawings. Though it is a little bit of a bummer that all of them have embedded fonts, even those that don't use text.

gameguy4313• 9 years ago

Oh iiinteresting I guess we are doing that! Probably not too hard to fix. Thanks for pointing that out!

They used to be just inline svgs (instead of img tags), but (at least a couple years ago) our research suggested using img tags was better for SEO and screen readers and even page load time.

edit: (Of course, when they were just inline svgs, they got the fonts for free from the surrounding webpage).

So far I'm thinking we'll just turn off the embedded fonts for images that don't have text. Definitely not expert on this stuff though--open to other advice!

cbzehner• 9 years ago

Interview cake is amazing. The way the problems are presented and the hints are given is often better than what you'll get in an actual interview setting.

After using it myself, I could not recommend it any more highly.

irl_zebra5• 9 years ago

Same here, actually helped me in real life a lot, worth the money. No affiliation with them. Their IDE sucks though.

gameguy4313• 9 years ago

:) New one is on the way! It's taken a while, but it's getting close.

andrei_says_2• 9 years ago

A small thing: the slide in subscription popover contains language which is dangerously close to the dark pattern of framing refusals as guilt/shame inducing.

A simple no thanks would do.

Because “they won’t remember what you did but hey will remember how you made them feel” and this made me feel “eww”.

gameguy4313• 9 years ago

Yeah, agreed. I'm thirsty for that install rate but more importantly I want us to be a force for good.

Fixed in master. Not freaking pushing while we're sitting at #1 unless I have to tho :P

Edit: Thanks for the note!

andrei_says_2• 9 years ago

You’re very welcome.

MattRix• 9 years ago

Agree completely! It almost made me leave the site without looking at any of the content, it felt gross.

partycoder• 9 years ago

I think these styles of puzzles borrow a lot from competitive programming (e.g: ACM, IEEE).

And while competitive programming requires skill, what you do most of the time is collaborative programming: create software that interoperates with other software, with a user, that is maintainable, etc. Software without these skills quickly becomes really expensive and hard to maintain.

Veedrac4• 9 years ago

One thing I find generally worth improving with these sorts of introductions is that they always seem to introduce data structures as a pick-and-mix bag of prebuilt parts, rather than a set of techniques which allow you to enforce properties which allow you to build objects that do what you want efficiently. Teaching the former is like teaching a physicist all the different kinds of gear systems, rather than the math that lets you model them.

Knowing how binary heaps and hash maps work is great, because binary heaps and hash maps are very useful data structures, but knowing the fundamental reasons behind them in a way that composes to building new things is much more useful. What happens when you want properties that someone hasn't already built a data structure for, at least as far as you can find? (Pet example: ordered container with efficient append and the ability to query the maximum of any subslice length k in O(log k). Extension: what are the minimal assumptions you need to do better, eg. amortized O(1)?)

I think this contributes to the attitude where programs are built out of monolithic, ill-fitting parts rather than actually looking at the problem and building the solution which does the right thing, the right way. (Pet example: if you designed websites as data structures and the browser to support doing so efficiently, 90% of requests on a site like Reddit would be a single `memcpy`.)

What I would attempt is rather than saying

"Here's one way we could do it: <explaination of pre-baked hash table>."

talk about the underlying tool first

"One tool that can help us is hashing: <explaination of general technique and why its properties are useful>. In this example we want <these properties> but can't immediately get it because our data has <these properties>. But we can apply hashing to get <technique that looks decent but has caveats>. Handling the caveats by doing <hash table things> gives us a data structure called a hash table."

Yes, this is probably a harder way to handle things, but I'd like to think it'd be worth the trouble.

chrisweekly• 9 years ago

That was a clearly-written, knowledgable, info-dense and effective bit of writing you just did, @Veedrac. Ever considered doing more of the same, and delivering the kind of educational material you just described?

Veedrac4• 9 years ago

I was expecting a far more mixed reaction, so I'm glad to hear this engaged people. Writing educational material to takes more work (and expertise) than I'd be willing to guarantee, but I'll keep the sentiment in mind :).

trishume• 9 years ago

You can subscribe to Veedrac's HN comments on RSS like I do. I've found a bunch of people like Veedrac regularly write really interesting things in HN comments, so I wrote an app that lets you subscribe to them: http://hnblogs.thume.ca/

catnaroek2• 9 years ago

Teaching the former is like teaching a physicist all the different kinds of gear systems, rather than the math that lets you model them.

Most programming work is less like theoretical physics and more like car repairing.

yawboakye2• 9 years ago

Programming is trial and error. Anybody who tells you otherwise is a salesman.

scottLobster• 9 years ago

I'm all for stuff like this in theory, but in my experience I never use said knowledge for any productive purpose and eventually it degrades... until I read a post like this, feel a surge of professional inadequacy and go re-learn it. :P

Dylan16807• 9 years ago

(Pet example: if you designed websites as data structures and the browser to support doing so efficiently, 90% of requests on a site like Reddit would be a single `memcpy`.)

You'd still want a compressed form, even if you had a good way to bypass parsing.

Veedrac4• 9 years ago

Ah, yes, I botched that description, since there has to be more to support things like encryption. A more accurate claim is that the bulk of the work currently done would be replaced with a memcpy.

petra2• 9 years ago

Can this be done using software ? can i ask some software/expert-system - i need this and that properties, and it can tell me - "use this structure" ?

devonkim• 9 years ago

I’ve wondered why we don’t typically use algorithms that will self-adjust when we have so many VMs that can do all sorts of statistical analysis. We know that quicksort is inefficient on smaller and mostly-sorted lists so we oftentimes switch to selection sort below 20 items or so, but we typically have libraries that have statically picked this behavior as directed by their developers instead of over time selecting the more appropriate algorithm. Sure, if you’be never seen the data before there’s not a lot you can assume, but if over a lot of executions your VM can perform native code substitution and replace certain sections of code out based upon runtime profiling in HotSpot why can’t we come up with heuristics that say “just use a list instead of a hash table until runtimes to access start getting slower than n, in which case reallocate the data to a hash table, btree, or a heap depending upon which operations are most sensitive to system design parameters.” A lot of problems seem like we’re repeating ourselves writing the base algorithms and gluing things together when we really should be investing problems around resource constraints and system trade-offs and priorities. Then we could run test suites against these systems to determine how well they’d meet certain guarantees programmed in.

amelius• 9 years ago

(Pet example: if you designed websites as data structures and the browser to support doing so efficiently, 90% of requests on a site like Reddit would be a single `memcpy`.)

Formatting a webpage cannot be done by a simple memcpy, especially since you don't know the size of the browser window in advance.

But perhaps I didn't understand the point you were trying to make.

Veedrac4• 9 years ago

I mean on the server-side. Right now the process between "I want thread 35va5k" and "I want to render this html" makes extremely inefficient use of both servers and network.

quickben• 9 years ago

A beautiful, amazing, and informative set of knowledge.

Sadly, an experience tarnished by the three, full page prompts for email subscription, right in the middle of the information flow.

neeleshs• 9 years ago

This looks good, but I prefer my copy of Algorithm Design Manual by Skiena.

victorhooi• 9 years ago

I was tempted to buy this - howevever, what turned me away was the subscription fee - it says:

No subscriptions to cancel—this is a 1-time charge. Access lasts (3 months) 1 year.

So sure - the fee may not automatically renew - but then you lose access to all the material after a year.

Is there not simply a way to pay for the course, and own a copy?

yawboakye2• 9 years ago

I've had the same concerns but I think--this is all my thoughts, no official sanction--Interview Cake started by catering to people who had interviews coming up, and so it didn't look like they will need more than a year's access. Neither would they need the material after they got the job. But I think @gameguy43 will see your comment and hopefully take it up with his team. I'd love to have eternal access, but then the 1-time charge might be bumped up too. Who knows?

nixgeek• 9 years ago

What kind of 'annual renewal' rate do you get at $199/yr?

Is there a good reason not to just do $199 lifetime?

hbk• 9 years ago

Take it easy with that email stuff. You say "no spam" but its literally spammed all around the page.

codingninja15• 9 years ago

@gameguy43, this is great guide. What resources were most helpful when constructing this guide? Any specific books?

The Intuitive Guide to Data Structures and Algorithms

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