Learn Hash Tables in 13 minutes

Hash Table tutorial example explained
#Hash #Table #Hashtable
// Hashtable = A data structure that stores unique keys to values
Each key/value pair is known as an Entry
FAST insertion, look up, deletion of key/value pairs
Not ideal for small data sets, great with large data sets

[@BroCodez]

import java.util.*; public class Main{ public static void main(String args[]) { // Hashtable = A data structure that stores unique keys to values ex. // Each key/value pair is known as an Entry // FAST insertion, look up, deletion of key/value pairs // Not ideal for small data sets, great with large data sets // hashing = Takes a key and computes an integer (formula will vary based on key & data type) // In a Hashtable, we use the hash % capacity to calculate an index number // key.hashCode() % capacity = index // bucket = an indexed storage location for one or more Entries // can store multiple Entries in case of a collision (linked similarly a LinkedList) // collision = hash function generates the same index for more than one key // less collisions = more efficiency // Runtime complexity: Best Case O(1) // Worst Case O(n) Hashtable table = new Hashtable(10); table.put(100, "Spongebob"); table.put(123, "Patrick"); table.put(321, "Sandy"); table.put(555, "Squidward"); table.put(777, "Gary"); for(Integer key : table.keySet()) { System.out.println(key.hashCode() % 10 + "\t" + key + "\t" + table.get(key)); } } }

[@ihateorangecat]

more python tutorials please bro🙏

[@ashutoshsoni9723]

Bro can you please make a video on Library Management System in JAVA. It's my request please!

[@masternobody1896]

nice

[@joyceasante8292]

import java.util.*; public class Main { public static void main(String[] args) { Hashtabletable = new Hashtable(10); table.put(254,"Irene"); table.put(802,"Derrek"); table.put(671,"Alonso"); table.put(545,"Veronica"); //System.out.println(table.get(545)); //table.remove(671); for(Integer key : table.keySet()){ //System.out.println(key + "\t" + table.get(key)); System.out.println(key.hashCode() % 10 + "\t" + key + "\t" + table.get(key)); } } } _____________________________________________ import java.util.*; public class Main { public static void main(String[] args) { Hashtabletable = new Hashtable(10); table.put("254","Irene"); table.put("802","Derrek"); table.put("671","Alonso"); table.put("545","Veronica"); //table.remove(671); for(String key : table.keySet()){ //System.out.println(key.hashCode() + "\t" + key + "\t" + table.get(key)); //System.out.println(key.hashCode() % 10 + "\t" + key + "\t" + table.get(key)); //System.out.println(key.hashCode() % 11 + "\t" + key + "\t" + table.get(key)); System.out.println(key.hashCode() % 21 + "\t" + key + "\t" + table.get(key)); } } }

[@pavanimaddala8060]

Can you explain how to create hash table in mysql

[@Aussiesnrg]

Was a programmer on a statewide court system back in the late 80's that needed a surname search to return a full page of results in less than a second. We used hashing tables and progressive searches to keep the speed amazingly fast. I think we had it down to about 0.2 of a second. They are fantastic with really large collections of data that needs searching.

[@marius.y6360]

Hey Bro, I just wanna thank you for teaching me all this stuff. 7 months ago I was almost nowhere not even knowing how to write a main method in Java but now I'm programming my own graphics library. You're truly a legend😎

[@blu5175]

whats a graphic library im new sorry

[@intifadayuri]

@@blu5175 libraries in java are a series of already build methods that you can use. For example, whenever you want to write something in the java console you need to import the java.util.Scanner library. My guess is that this guy is talking about a library to build a 3d engine with java

[@blu5175]

@@intifadayuri Yea I learnt this by now it's been 11 months! Haha but still thank you very much?

[@AMZ_official]

@@blu5175 It's been 11 months again! did you complete it? What else have you achieved in your career? Asking for just motivation

[@RonnieBanerjee007]

​@@intifadayuri well, you tried to help, that's what counts ❤

[@dmitriivlasov3728]

Bro, We just started going through Hash Tables in our CompSci class and now you release a video. Thank you!

[@WorkSmarter__]

Level of teaching of Bro is just on another level👍

[@thomashansknecht1898]

I am surprised my computer science curriculum barely even mentioned hash tables. They have been such a game changer to me at work as a software engineer. Way faster and easier than using an array and nested loops.

[@randomrun1]

That's interesting, I'm about to start my BSCS and I'm pregaming with the popular Java MOOC. It has an explanation of how to use hash tables in the 8th week and how to make them from scratch in the 12th week. Glad I got the info there if it's not going to be in my curriculum.

[@clashclans9783]

that actually makes so much sense!! was looking at the profssors notes and watching his lectures and not understanding it one single bit!!!! long live the BRO!!!!

[@VERY_TALL_MAN]

Wow, this is a really good introduction to hash tables!

[@BroCodez]

thanks Grayson!

[@deepakr1945]

@@BroCodez it bad

[@elielvieira3041]

@@deepakr1945 nah

[@windigo77]

It's too bad it violates the ADA with its use of camelCase for method names, and is therefore an illegal language to use in the workplace

[@crossfadez5521]

This was a very insightful video, thanks a lot. Although I really wished you also went over how to treat a bucket as a linked list and iterate through it to find the key you're looking for.

[@PratikThisSide]

Simply, subtly & nearly explained Bro Sir 👌🏼 #KeelItUp ✌🏼 #LoveFromINDIA🇮🇳

[@dbvs007]

Thank you, I have been having questions on HashTable and wanted to understand hashCode, excellent explanation, keep doing more videos.

[@hwstar9416]

Things to note: If you have collisions the best course of action is to change your hash function. In your example, a good hash function would be taking the ascii code of the rightmost number and subtracting 48, that way you'd have 0 collisions and don't need to do % anymore. Another thing, if your table size is a power of 2 you don't have to do % anymore, you can instead do bitwise and with table size.

[@mikoalt]

Can you explain the bitwise with table size if the power is 2?

[@ThomasEdits]

I just found out about hashtables so I would appreciate some input: If you are using a hashtable for storing dynamic data, how would you know what hash function always guarantees no collisions?

[@hwstar9416]

@@ThomasEdits your data is never truly random. You can always make your hash function avoid collisions (not always completely) by analyzing your data and coming up with a good hash

[@oogshow2809]

It’s beautiful lecture I like this hash , I’m always favourite your lecture bro due to your best explanation , keep going bro

[@ruleoflawedutainment]

I studied this last term but didn't understand what I do now. Thank you.

[@patriciale6647]

I didn't pay attention during lecture and I have a quiz tomorrow, so this is a lifesaver!

[@umut_satir]

i didn't understand the other videos but you clearly explained how it works, thanks for the content

[@aryankumar313]

Brooo!!!!....you just explain so good!....got it just by watching it once!

[@mjjrr1331]

Simple and understandable. Thank you so much for this tutorial!

[@daviduntalan]

thank you for this tutorial, now i can finally understand the HashTable.

[@stephanieezat-panah7750]

As always, an excellent presentation. thank you

[@joeyfarrell4399]

I love this channel so, so much

[@robdimmitt3204]

Unbelievably good video

[@collectick]

Better explanation than my computer science teacher, and my native language isn't event english! :)

[@mistersir3185]

good surface level info

[@P0K0]

The best video I've seen today ❤

[@stillpickinganame5350]

Very good, thank you!

[@eugenezuev7349]

sweeet

[@maggiemauno]

I love youuu🥺🥺 Respectfully BUT sincerely Many thanks!

[@ldpenrose]

The BRO is BACK!

[@alexh3143]

the only video I found that has explained hash tables clearly

[@abdalwahedhajomar3898]

This video is amazingly helpful

[@TheFlexath]

thank you sir , best explanation.

[@Mohamed-uf5jh]

Good explanation . Liked it a lot !

[@tavwalt1973]

Wow thank you so much, this was super clear!!!!

[@acatisfinetoo3018]

Hash table is my favoriate data structure😉

[@khushalsinghsaini805]

how we can deal with HashTable of Classes? Like in place of int and string key it is some sort of class. Like Hashtable;

[@skillR-243]

Thanks for this videos Bro!

[@ChristianRodriguez-tm3jg]

thanks bro... greetings from Ecuador

[@Code_JAVA268]

tooo cool man

[@wrizu]

how do you access a vlue from a bucket it only shows the head (first) value.

[@mohitjain957]

bro you are insane Thanks sir I really appreciate

[@akmalbukhariev7932]

Thank you so much sir.

[@ethio15code]

Nice explanation 👍

[@punzalanchristine2442]

what do you call when u give that type of solution in collision, is it open hashing or not?

[@mugosimon717]

you are the best

[@hypnos9336]

helpful, thank you

[@callmesuraj4257]

Bro 🤩 Tq 4 your Quality coding Video. & Now i am busy with your python 🐍course. Tnx again ☺️. Bro ✌️🎈✌️

[@ztipster]

Does google uses hash tables to display instant results ?

[@flammabletfm3405]

Wow! Nice.

[@facuz4170]

Nice video!

[@lucacodastefano2409]

Very nice lesson, like every other!

[@hazmi96]

Thanks! love your videos!

[@danielhowe3393]

Could you go over the A star algorithm next pls

[@kosolomon123]

good quality content!

[@coder4937]

Good work👍👍👍👍

[@katendetimothy6542]

Bro thx for the free videos. How can I apply this topic in real life maybe in GUI?

[@justinbanza4079]

Thank you for this video

[@DINESH-ji7tm]

Sir , please provide use app development course , It's a very helpful .

[@hermansiisengbae]

Wow 👍👍

[@bluekrazykris]

What's the difference between Hash tables and hash maps?

[@migelangelcarrillo1710]

@@dispatch-indirect9206 he/she asked for the difference, not your opinion on the subject

[@trevorphilipsindustries1046]

I'm wondering if these hashcodes been written incorrectly here 3:49 Because the hashcode of String "100" would be 47155, not 48625. and here is why: Initialize hash to 0: hash = 0. Multiply hash by 31 and add the numeric value of the first character '1': hash = (0 * 31) + 49 = 49. Multiply hash by 31 and add the numeric value of the second character '0': hash = (49 * 31) + 48 = 1517. Multiply hash by 31 and add the numeric value of the third character '0': hash = (1517 * 31) + 48 = 47155. so, am I right, these numbers in the example's hashcode are just random numbers and have nothing to do with the righ hashcodes?

[@SaiMoen]

10:15

[@jeonjungkook-vu4fg]

i HAVE MY FINAL EXAM IN TWO DAYS.... I HOPE I PASSS

[@hasinulhudaenu8098]

Did you pass??

[@mostafayounes9490]

Thank you ❤

[@nageshmh]

Awesome

[@MrLoser-ks2xn]

Thanks!

[@emiralpkilic5669]

Eyyo Brooooo you are a legend!!!

[@KiranNaragam]

GOAT Video of HashTable

[@SlashKilll]

THANK YOU YOU SAVED ME

[@touzaikokon]

thanks bro

[@Heyleang]

Thank man

[@TylerBriggs-m2y]

Well done, TY!

[@thedojoclub]

thank god for Bro!

[@victorrezende6002]

Nice class

[@gerxisander5294]

very nice tutorial. BIG LIKE

[@jimmy2055]

wish u did this in c++

[@visitor404]

Bro 🤜🤛

[@ruthvikas]

@Bro code, it would be great if you teach android development with kotlin also...

[@hyvaahyvaa9578]

hi is it possible to implement the hash table using an array?

[@owlexb1124]

Thank you!

[@vishnuskandata2355]

isnt it just jumbling the order? how is that more efficient? I'm confused.

[@getyournekoshere9824]

nice vid man thanks

[@BioDeus]

I was thinking the table size should be a prime to reduce collisions, no? Should have tried 13 first.

[@YDV669]

Back in Image/3000 days(70s, 80s, 90s, early 2000s), master tables(manual and automatic) were hashed with collisions resolved exactly as in this video. The rule was to create such tables with a capacity of a prime number. If you need a million rows in your table, set the capacity to the next prime number. it wasn't enforced by the database, actually, but later, utilities were created to help in resizing tables and these would actually tell you what your capacity should be based on what you requested.

[@schifoso]

Make hash table size a prime number.

[@heavenlypenguin6613]

Thank you Bro!

[@user27108]

how many programing languages you know?

[@firepower01]

Thanks Bro

[@DesiredFactsDaily]

Bruh I am from pandora huge love and want to take you to my planet and our avatar.jr too learn ds to crack FANG companies

[@xinfangmin3665]

Never be so early！

[@dennismc8145]

I love you

[@ox6542]

Functions as a map

[@huyngo2u924]

heap sort, please

[@juanpunch8473]

data structure is far more easy in java compare to c++ :

[@karlostj4683]

"...divide it by the capacity of our hash table, and find the remainder..." Except that's not what the narrator is actually doing - the narrator is just doing the modulus without doing the division. Why?

[@karlostj4683]

For the entry ("100", "Spongebob") hashing "100" --> 48625. 48625 divided by the capacity --> 4862. 4862 modulo 10 --> 2. But what the narrator did was "100" --> 48625 then 48625 % 10 --> 5.

[@oe7356]

@@karlostj4683 48625 / 10 = 4862 remainder 5. Modulus directly computes the remainder.

[@X_Potato]

I dont understand something here, how does searching actually get faster? if you dont know the key or the index how is it different from not knowing the index in an array?

[@XxxxTxTxxxX]

If you don't know the key then you would have to iterate over the hashtable. If you're performing those kind of searches then just don't use a hashtable. A search tree would be a better choice

[@kylebelle246]

You should always know the key. and since the index is just calculated by the key you also inherently know the index. searching only kinda comes into play if there were collisions and in that case you are now searching a much smaller subset opposed to an array where you would be searching, possibly, the entire array.

[@kylebelle246]

in this example he used numbers as keys, but in the real world you'd probably use the name as a key (e.g "spongebob") and then store some sort of object (or any type of data doesn't really matter) as the value. The key isn't supposed to be just any random/arbitrary value, it should have some meaning in your context

[@FranklinBegley-f1x]

Lee Karen Robinson Elizabeth Brown Sarah

[@apmcd47]

Wait, Gary Seven?

[@v.f.38]

Teach golang.

[@immortalbotyt1428]

Cmon C# is not bad either u can't ignore a good language what can be used to create android ios apps , with xamarin , can used to develop OP games at unity and so on cmon bro plssssssssssssssssssssss

[@junaidrashid7525]

pever

[@alpeshamriwala1740]

Thanks bro 😭