Hash Tables and Hash Functions

This computer science video describes the fundamental principles of the hash table data structure which allows for very fast insertion and retrieval of data. It covers commonly used hash algorithms for numeric and alphanumeric keys and summarises the objectives of a good hash function. Collision resolution is described, including open addressing techniques such as linear and quadratic probing, and closed addressing techniques such as chaining with a linked list.

[@ryanbutterfield5038]

You deserve my data structures professor's salary

[@ComputerScienceLessons]

Why not send him a link to my channel :)

[@annellysemathison2179]

mine too. serves no purpose

[@tushar6742]

Ha ha ha rofl

[@SamKhan-kb3kg]

Bang on, I was thinking the same :-)

[@alexanderbergkvist9224]

Haha x) Great video Kevin!

[@ThePandaGuitar]

Your voice sounds like a National Geographic documentary. Amazing explanation! Subscribed.

[@Wow55579]

This guy taught me ict when i was little trust me he sounds just like it

[@joerj2460]

ThePandaGuitar he’s my computer science teacher

[@Peter-wm7fj]

His British accent sounds so cool!

[@rmapatipandey9217]

😂😂😂😂😂😂😂

[@coob404]

he sounds a little bit like Tom Scott

[@MartinBojmaliev]

Before 14 minutes, I thought I will never understand Hash Tables. Good work and Thank you.

[@ComputerScienceLessons]

They are actually quite simple in principal aren't they! Thanks for the comment.

[@MartinBojmaliev]

We got the reason here why they are used and how ... then it's very easy to use them in the right way !

[@maybecrazy6934]

same here, this video is so cool.

[@stefanshapkarov184]

Exactly sir, very good video indeed.

[@atanasatanasov5119]

He is a life saver isn't he?!

[@nap163020]

Why did I spend all that money on an engineering degree, when all I needed was this channel!!!

[@ComputerScienceLessons]

Thanks for the complement. University does have it's benefits :)KD

[@mrwess1927]

This is what youtube is for. Just a clear explanation of interesting ideas. +1

[@MisterWessells]

CAKE BAKING kzbin.info/www/bejne/eqSce5uraqpkqas&ab_channel=MisterWessells

[@joegarza8391]

Years after, this video is still immensely valuable. This is what teaching is supposed to look like. Thank you for your amazing work!

[@ComputerScienceLessons]

Thank you. Crikey! that was uploaded nearly 5 years ago! :)KD

[@ThunderAppeal]

There are so many things wrong with this 'explanation' I'm not surprised that a half wit like you is impressed by this video. You defininetly have no idea what he is saying here. And he is talking utter nonsense.

[@TheeSlickShady]

This video So clear and easy to understand Thank you 🏆🏆🏆

[@ThunderAppeal]

@@TheeSlickShady You understood nothing so you can stop pretending.

[@TheeSlickShady]

@@ThunderAppeal haha got me!

[@hotlinkster123]

"indices are calculated from the data" thats literally all I needed to understand hash tables but surpirsingly I've never heard it once when people have mentioned them. Of course the bit on how to handle collisions was useful as well

[@ComputerScienceLessons]

Exactly - that is the essence of a hash table - it's that simple. A basic understanding of how physical RAM works explains why one memory location can can be accessed just as quickly as any other. :)KD

[@saikumar2385]

Same for me

[@das6109]

For me that part was intuitive, but I didn't understand how you would deal with that process creating multiple entries in the same index. This video was a big aha moment.

[@Fandrir]

That is exactly what i thought. Exactly that one piece of information that i was missing. I have no idea why that was never made clear anywhere else i looked.

[@tweedyburd007]

You actually explain it as if we've never heard of the concept before! Something a lot of CS professors seem to not understand...

[@utsabshrestha277]

Now this is a real education , so well described, you got the real tallent sir, really appreciating. You teaching approach can make anyone from zero to hero

[@abdullahakram4942]

you basically summarized 3 whole lectures of class into just 14 minutes. You're a life saver!

[@kola844]

Professors should just play videos like this at the start of class. Would improve student performance immensely.

[@lucianojadur]

I've never thought I could find such well presented and easy-to-follow explanaition about this topic in less tan 15 minutes. It's a gem among stones.

[@tinojaa6749]

In a perfect world every teacher would be as clear as this guy :)

[@ComputerScienceLessons]

You are very kind :)KD

[@samanthacrespo5745]

Agreed!

[@neeyatiajmera869]

By far one the best explanation videos I've ever watched. The most useful 14 minutes of my life. Thanks!

[@ComputerScienceLessons]

Glad to be of help. Thanks for the lovely comment. :)KD

[@victorboateng5449]

This was posted 5 years ago but I can say it is still relevant today. Appreciate the wonderful explanation

[@ComputerScienceLessons]

Thank you :)KD

[@deancj1]

This is the clearest, most concise explanation of this structure I've come across. Thank you! A lot of people really muddy this subject up.

[@ComputerScienceLessons]

Thank you :)KD

[@m.l.c.m.madhawa4649]

Yes I was also going to tell that, this is the clearest and most concise explanation I've come across

[@Lexoka]

The video is very, very, very well made. That's a great deal of information in just under 14 minutes, and it is very clearly presented. You've more than earned a new subscriber.

[@kevin_machine_learning]

Some Profs can, of course, explain what is hash table, but you just do that in about 10 mins!!! Your explanation is so clear and easy to understand, I think that is what students are looking for! Thank you Sir!

[@kuyabongekamayeza1751]

I come across this page today. A game changer, I tell you!!!!!! Thank you sooo much.

[@ComputerScienceLessons]

You're very welcome :)KD

[@kubamaruszczyk4043]

The best explanation I have encountered so far. Thank you!

[@insofcury]

This just cleared every possible doubt that I could possibly have related to hash tables.

[@WaqasAhmadVlogs]

Holy shit! You made it sound like a piece of cake. I've been hearing about hash tables for so long and always thought it must be a rocket science until now. Hats off to you sir

[@BorlandC452]

I've been watching quite a few hash table videos lately. This is the best one I've come across.

[@m.l.c.m.madhawa4649]

This is the clearest and most concise explanation I've come across

[@sujithav8871]

very good explanation. after a long time, i found a good lecture for hash table. thank you so much for your wonderful lecture

[@ryanbarry7670]

Better explanation than my tutor did in 3 hours! So cool, thanks for posting the video!

[@chasingthestereotype6420]

thank god you decided to record youtube videos. You just destroyed my fear of hashing in under 15 minutes, you have my eternal gratitude

[@6locc6a6y_fps]

holy legend, i have 2 days left for my data structures project and you just saved me so much time. BIG LIKE

[@ComputerScienceLessons]

Delighted to help :)KD

[@charlesbaldo]

I just found this. As a professional with 30 year experience with data analysis you are spot on, well explained. I subscribed and set notifications on, hope to see plenty more from you.

[@lanat4260]

I spent hours trying to understand this for my final exam tomorrow to no avail. Until i came across your video! Thank you so much for this :)

[@felizdeannemayao4811]

I love how excited, eccentric and passionate he sounds. Sounds very motivating for me!

[@navidmohammadzadeh2141]

I liked what you have prepared to introduce what is clearly hashing algorithms is. Of course, I would watch it again and again.

[@jannesvanquaillie9151]

This is a SUPER good video. I've always wondered how hash table worked. But I didn't think it was this genius.

[@arielspalter7425]

Fantastic tutorial. Just perfect pace, perfect intonation, perfect graphics and perfect depth to explain the topic to non-educated programmers like me. Subscribed!

[@patrickd791]

Really eloquent description of the subject. This is the first time I feel like I actually know something about Hash Tables. Thank you.

[@AshishSingh-gb1yv]

This is neat, well structured and excellent video for any developer to understand HashTable and gives a fair idea about HashMap concepts. Absolutely fabulous work done !!!

[@monishagowda8928]

And that's how you teach!!! Thank you so much for such a clear explanation 😊

[@casanovavzla]

You just got me like 1:30 hour of sleeping instead of having to search the entire internet.... Thanks a lot! Suscribed!

[@jorgeramos9350]

I have reviewed several KZbin explanations about hash tables and hash functions, and none come close to this one. It was clear and to the point. Great job and thank you!

[@usamamushtaq703]

i have been searching on youtube for almost an hour but couldnt find an appropriate video of explanation of hash table until i find this video .....beautifull explanation

[@keeperkell13]

I don't normally comment on videos but this was the most helpful explanation of what a hash table is and how to use one. I have been looking for good articles and videos for a couple of hours before I found this video! So thank you!

[@ComputerScienceLessons]

Thanks for talking the time to comment :)

[@polomame]

I don't normally like videos on youtube, but you helped me understand this concept.

[@ironbob11]

Described way better than all the other videos I've seen on this topic. Thank you

[@conermos]

A big thank you. 2 hours of lectures couldn't explain what you did in 1 KZbin video.

[@ComputerScienceLessons]

You are very welcome :)KD

[@LandNfan]

Excellent video! I spent the last half of my 34 years in IT working with the Advanced Pick and Unidata databases which depend heavily upon hashed access. The key to efficiency is selecting the right modulus when creating your file. Too small and you get too many collisions, too large and you waste space. The multivalue database concept goes back to the mid-60’s, but it is still hard to beat for efficiency and ease of use.

[@VolkWasHere]

Give this man a Medal, thank you!

[@mubafaw]

Absolute legend. The best introductory video I have seen so far on Hash Tables and Hash functions. Thank you, Thank you, Thank you 😊😊😊

[@ComputerScienceLessons]

You're most welcome :)KD

[@charbelalam2648]

You literally are the only person to ever make me understand this mess. Thank you so so much!

[@ComputerScienceLessons]

I'm delighted to help :)KD

[@rebeccataylor8188]

Never heard someone so hyped about hash tables, but I love it. Thanks for the great explanation!

[@ComputerScienceLessons]

It's a Sunday morning pastime.

[@herokim5113]

You are the best voice actor in CS. You deserves it!

[@yukeyang5735]

Very hard-core stuff, yet very easy to digest. You are a genius.

[@TaylorColpitts]

Great breakdown and very well illustrated - it's been a while since I've used these. Thanks!

[@daniloradulovic7646]

Basically i listened 2min of your video and i understood everything good job man!

[@safedupkid]

Excellent explanation. Appreciated the clarity and succinctness

[@tigerslashii7097]

This was incredibly straightforward and easy to follow.

[@CarlNeuDitters]

Fantastic. Not only did you lay out the problem well, and explain how hash tables work but you even set a good example of what any kind of teaching should be.

[@jenjen3]

Great video, I'm totally new to this and actually understand hashmaps now. Thank you so much!

[@cogs11]

This was a great explanation ! I was even imaging how this could be coded.

[@stocksking8372]

What??? This is probably the most insane condensation of information I have ever seen. My professors put up a 2 hour lecture, with an additional 1 hour lecture of extra material if we needed it. Had no fking idea what they were talking about. This video, I completely understand it. Thanks.

[@ComputerScienceLessons]

Thank you for the complement. Maybe you should send your professor a link to this video :)KD

[@stocksking8372]

@@ComputerScienceLessons Haha perhaps, or at least to the others taking the course

[@ashutoshmane3513]

it was one of the easiest explanation i had witnessed to something, without letting go the jargons. great subscribed

[@MdMainuddinJU]

This is one of the best lectures I have ever found to understand something clearly and precisely, yet in a reasonably short time.

[@intrepidsouls]

That is what we call a man born to be a teacher.

[@zhechen4814]

Demonstrated the concepts incredibly well!

[@plekkchand]

Proper explanations, logically and clearly expounded, in comprehensible English. This sort of material is by no means easy to find.

[@ComputerScienceLessons]

Thank you. I need to work om making it easier to find. :)KD

[@arlene5990]

omg i love your voice and your explanation it’s really clear, thank you!!!

[@kazimafzal]

Loved the concise yet thorough explanation! More vids like this one please! Subbed!

[@kardelenbuz450]

ı've been listening for a whole year from my professor and couldnt understand any of these... now even i cant believe that i got the point . thank you so much

[@kalanaherath3076]

I absolutely LOVE your channel! it really helps me with my A level ICT studies! Thank you! I am eternally grateful!

[@Democracyphobia]

ok this was brilliant . we need more teachers like you . understanding whats going rather than just learning by heart .

[@ComputerScienceLessons]

Thank you so much :)KD

[@sushruttabakade6088]

Tens of books couldn't teach me what you just did in a couple of minutes. you are fantastic!!!

[@unitedtomato5444]

I like how he speaks without any pauses or mistakes.

[@ComputerScienceLessons]

Thanks. I usually script it first :)KD

[@mudshovel289]

Thank you so much dude. So. Much. Imagine reading this in a textbook and nit understanding anything because it’s a bunch of text and you’re in an online class.

[@ComputerScienceLessons]

You are most welcome :)KD

[@stephan553]

One _very important_ case against open addressing is that any case where the key is not contained in the hash map can only be resolved in O(n) time, that is a time linear to the length of the whole map. Closed addressing can resolve this by simply traversing the much shorter list at the respective key. No matter if databases, caches or many other use cases, looking up a missing key is a very common situation.

[@your-mom-irl]

That shouldn't matter much if the load factor is kept low and the hash function has a good distribution, but yeah it is a possibility lol A uniform distribution with 50% load factor will give you an average of just 1 miss

[@charlliemurphy8381]

this dude saving lives in 2020

[@TonyKingOfTheOzone]

CS 260 student here and Chat GPT recommended this video. I can see why, this was so helpful as someone who literally has never coded a hash table into a project yet this video is exciting to see how I can store data and access it. Now I cant wait to start coding this into a project!

[@ComputerScienceLessons]

Delighted to help. It's interesting to hear I have the attention of chatbots. :)KD

[@RahulTandel]

Thank you for the clear and concise explanation without making it sound like we're studing rocket science.

[@ComputerScienceLessons]

You're welcome :)KD

[@mushusax]

The examples he uses are real. Ex: Bea = Beatrice Tinsley; created galaxy models Ada Lovelace = Ada Lovelace; the first programmer

[@ComputerScienceLessons]

Mostly... Beatrice Tinsley (Astronomer) Tim Berners Lee (Computer Scientist of WWW fame) Leo Adelman (Mathematician of RSA fame) Jan Łukasiewicz (Logician of reverse Polish notation fame) Lou Kauffman (Mathematician - of polynomial fame) Max Newman (Mathematician and code breaker) Ada Lovelace(Computer Scientist) Ted Nelson (Computer Scientist and Philosopher) Sam (Sam Malone - the guy in Cheers) Mia (the space station) Zoe (Zoe Saldana - Guardians of the Galaxy, Star Trek)

[@Afdch]

@@ComputerScienceLessons Except the space station is MIR, not MIA. Just saying.

[@ComputerScienceLessons]

мое орфографическое отстой

[@SJ23982398]

Yeah and Tod is real too. Tod Einstein. Famous for drinking a relatively large amount of beer in a very short amount of time.

[@charlesbaldo]

M Detlef she died. A life of debauchery is often short.

[@GoddamnAxl]

You sir deserves a medal;

[@ComputerScienceLessons]

I'm still waiting for the queen to get in touch. :)

[@DJNecktron]

Thank you good sir for this splendid and easily understandable video! My hopes for the "Data structures and algorithms" exam are looking way brighter now!

[@PENCILARTAbhishekHimanshu]

can't stop myself to like this video. obsessed with the explanation

[@ComputerScienceLessons]

Thank you so much :)KD

[@ahmedshalaby948]

I just stumbled upon your video and I must say, you did an amazing job! Your clear and concise explanation helped me understand the concept better than any textbook or lecture ever could. Your use of examples and visual aids made the topic so much easier to grasp.

[@ComputerScienceLessons]

Thank you so much. I really appreciate comments like yours :)KD

[@AhmetHDonmez]

Just incredible, thank you for your time and efforts for these incredible videos. Your teaching abilities are through the roof!

[@ComputerScienceLessons]

You are very kind :)KD

[@fritsgerms3565]

nicely done. I have decades of experience with hashing and it's nuanced properties that very much depends on table sizes, types of keys, types of implementatios, the key values themselves, different hardware, etc, and I would not have thought that in 14min an explanation could be so comprehensive with some insights given. well done.

[@neonoply2205]

A wonderful explanation which resolves all my questions.

[@katariegels258]

You already got tons of love in the comments, but you deserve one more. Very well explained with simple, yet very useful, animations. Thank you very much for the great work! :-)

[@ComputerScienceLessons]

Thank you. Comments like yours make my day. :)KD

[@TheInertBoyz]

That's perfect explaination....

[@FidelSantana87]

The best professor I've ever listen in my entire life!!!!

[@geybriyel2416]

finally, a clear and great visualization of the hash table. Thank you so much, this has been really helpful for me to understand the principle.

[@ChrisBreemer]

Excellent, crystal clear, perfectly animated and optimally paced. Many thanks ! What I missed were some simple ideas to improve the hash function to reduce collisions. I could think of factoring in the position of a letter, so that 'Leo' doesn't collide with 'Loe'. Maybe also the length of the string though that's of no use in this particular example. Also it would be great to have some examples of how to choose between closed and open (and the different variants of open).

[@AdiPrimandaGinting]

You have a fine English accent, Mate. It helps my brain gear run smooth

[@Maadhawk]

He sounds like the guy who presents "Explaining Computers", and if he is the same guy, wouldn't surprise me one bit given the topic of both channels.

[@MisterWessells]

CAKE BAKING kzbin.info/www/bejne/eqSce5uraqpkqas&ab_channel=MisterWessells

[@sandipanbera]

This is a video of a different level. Hats off to you Sir.

[@jsonslim]

After checking several hashmap lessons I want to say that this is the best one

[@holdenmcgroin8917]

I had a light bulb moment after only 3 minutes into this lecture... amazing! Thanks!

[@ComputerScienceLessons]

It's all about light bulbs. :) KD

[@reca117]

Your videos are amazing quality. Keep it up

[@ComputerScienceLessons]

That's great to hear - Tnx

[@osamaa.h.altameemi5592]

Best explanation so far and the animations are so on point. thank you for making data structures enjoyable again :)

[@cloudproblemssolved]

It makes so much sense, you translate each letter to ascii value before adding em up and getting the remainder of the letters’ values summed up divided by total number of squares (e.g. 11)

[@ron0studios]

this is the most beautiful explanation of hashing I've ever come across. Well done! All the other vids take a cryptic description and focus more on big ideas like blockchaining and encryption/security. Having a nice bit-sized chunk really helps out! Thanks!

[@ComputerScienceLessons]

Lovely comment. Thanks for making me smile :)KD

[@pranavnyavanandi9710]

I would like it if videos like this transitioned to such bigger concepts after giving a good foundational understanding like this. Would be real helpful, especially for beginners looking to advance.

[@GunelMammadova93]

The best explanation of hash tables/functions! Thank you!

[@parthvirana4148]

Some people are amazing coders but not amazing at explaining, and you are the exception

[@ComputerScienceLessons]

You're too kind. Thank you :)KD

[@ajayreddykanduru453]

Very fortunate to find this great KZbin channel

[@ComputerScienceLessons]

Thank you :)KD