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)); } } }

[@54peace]

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

[@Proletariat-intifada]

@@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]

@@Proletariat-intifada 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]

​@@Proletariat-intifada 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!

[@mjjrr1331]

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

[@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

[@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!!!!

[@WorkSmarter__]

Level of teaching of Bro is just on another level👍

[@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.

[@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.

[@dispatch-indirect9206]

_I am surprised my computer science curriculum barely even mentioned hash tables_ From interviewing people, this seems like fairly common practice in CS. But chasing buzzwords is devaluing CS: these fundamentals are what distinguished a four-year degree from a coding bootcamp.

[@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.

[@PratikThisSide]

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

[@confused6526]

Oh My Goodness... The best video on HashMap data structure. You're the man! 👍

[@dbvs007]

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

[@gerxisander5294]

very nice tutorial. BIG LIKE

[@umut_satir]

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

[@stephanieezat-panah7750]

As always, an excellent presentation. thank you

[@nischalofchrist]

Bro, you Rock. Best and simple explanation of Hash tables. Thanks

[@patriciale6647]

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

[@abdalwahedhajomar3898]

This video is amazingly helpful

[@ruleoflawedutainment]

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

[@daviduntalan]

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

[@randomrun1]

This is a great video, thank you. It's much clearer than my course material.

[@oogshow2809]

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

[@aryankumar313]

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

[@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

[@lucacodastefano2409]

Very nice lesson, like every other!

[@hazmi96]

Thanks! love your videos!

[@robdimmitt3204]

Unbelievably good video

[@rmsoft]

Really good, no babbling, just information.

[@mistersir3185]

good surface level info

[@TheFlexath]

thank you sir , best explanation.

[@recipeFor]

Thanks a lot for providing a valuable video.

[@tavwalt1973]

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

[@joeyfarrell4399]

I love this channel so, so much

[@ethio15code]

Nice explanation 👍

[@Mohamed-uf5jh]

Good explanation . Liked it a lot !

[@victors8718]

Bro is an absolute legend

[@acatisfinetoo3018]

Hash table is my favoriate data structure😉

[@zeeg1529]

top quality content. great job, Bro!

[@mohitjain957]

bro you are insane Thanks sir I really appreciate

[@P0K0]

The best video I've seen today ❤

[@joseoterol]

I love that man. Thanks mate

[@gamermachine4048]

Nice, can you make a video on suppliers and consumers next?

[@akmalbukhariev7932]

Thank you so much sir.

[@ldpenrose]

The BRO is BACK!

[@ztipster]

Does google uses hash tables to display instant results ?

[@kosolomon123]

good quality content!

[@skillraiderv5289]

Thanks for this videos Bro!

[@jordimorenosanchez584]

I thought I understood what a hash table was till I saw this video 🙏

[@ChristianRodriguez-tm3jg]

thanks bro... greetings from Ecuador

[@justinbanza4079]

Thank you for this video

[@hypnos9336]

helpful, thank you

[@user-ss2rt9xk4g]

Well done, TY!

[@patahgaming]

I learn how to use hash table without tutorial now :)

[@margretmauno1285]

I love youuu🥺🥺 Respectfully BUT sincerely Many thanks!

[@punzalanchristine2442]

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

[@ukaszkiepas57]

thank you bro. Student from Poland :>

[@danielhowe3393]

Could you go over the A star algorithm next pls

[@DINESH-ji7tm]

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

[@Piseth_01]

In cars stuff we have Chrisfix in computer stuff we have my bro right here.

[@SlashKilll]

THANK YOU YOU SAVED ME

[@mugosimon717]

you are the best

[@emiralpkilic5669]

Eyyo Brooooo you are a legend!!!

[@hyvaahyvaa9578]

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

[@Code_JAVA268]

tooo cool man

[@katendetimothy6542]

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

[@ruthvikas]

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

[@xxmsdxx]

Keep going ❤

[@flammabletfm3405]

Wow! Nice.

[@heavenlypenguin6613]

Thank you Bro!

[@facuz4170]

Nice video!

[@owlexb1124]

Thank you!

[@StephanHaloftis]

Is it possible to design the table to have a dynamic capacity that can be adjusted if there are collisions?

[@kylebelle246]

i could see this taking more work and end up being slower than just appending to the linked list, since you the existing element now also need to be moved since their table index may no longer be the same give the remainder will likely be different. i would say just make sure the hashtable is sized appropriately and at that point you've done the best you could

[@coder4937]

Good work👍👍👍👍

[@alanfrost2973]

Another day Thank you so much if you ever have membership for no reason ill try to join to money you deserve it

[@hermansiisengbae]

Wow 👍👍

[@elias6406]

What’s the difference between hashtable and hashmaps?

[@HarryInShape]

I love you Bro

[@alimasterchess778]

Bro can you please do assembler tutorial videos?

[@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;

[@getyournekoshere9824]

nice vid man thanks

[@victorrezende6002]

Nice class

[@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

[@SnackPacks10]

Can you find the values in your hash table from its address?

[@issac17]

Thanks man I really appreciate ❤️

[@BroCodez]

anytime! Thanks for commenting

[@issac17]

Your videos are really helpful...you deserved it❤️

[@visitor404]

Bro 🤜🤛

[@adheesh2secondsago630]

Nice👍

[@user27108]

how many programing languages you know?

[@MrLoser-ks2xn]

Thanks!

[@ngndnd]

so its the exact same as a hashmap?

[@filipedlund7038]

What to do when the ids of students are the same? Thanks

[@koctarac]

Do you have a patreon or paypal for us to donate?

[@gksw_g1437]

thanks!

[@touzaikokon]

thanks bro

[@firepower01]

Thanks Bro

[@thedojoclub]

thank god for Bro!

[@alpeshamriwala1740]

Thanks bro 😭

[@joseluizdurigon8893]

Ok, but the bucket we're talking about is a memory address? I mean, if we have a collision, we must create a linked list. Fine with that I get it, but that linked list will be stored in the same memory address? I don't think I'm rationalizing right. The linked list will be stored like a vector and the data that has a collision will have a pointer to that new node right? I'm sorry if I sound a little bit confusing but that's what I've figured out

[@kylebelle246]

What if it was always a linked list? even if there are no collisions and the linked list only contains one node. I think that'd make more sense

[@jimmy2055]

wish u did this in c++

[@bluekrazykris]

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

[@dispatch-indirect9206]

The short answer is you shouldn't use Hashtable and this video shouldn't recommend Hashtable, though this confusion is partly on Oracle. The original collections, especially Hashtable and Vector, were all made to be thread safe. This was only useful in specific cases and the method of making them thread safe was not performant. Per the API docs for Hashtable: _As of the Java 2 platform v1.2, this class was retrofitted to implement the Map interface, making it a member of the Java Collections Framework. Unlike the new collection implementations, Hashtable is synchronized. If a thread-safe implementation is not needed, it is recommended to use HashMap in place of Hashtable. If a thread-safe highly-concurrent implementation is desired, then it is recommended to use ConcurrentHashMap in place of Hashtable._

[@migelangelcarrillo1710]

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