Quicksort Sort Algorithm in Java - Full Tutorial With Source

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2 жыл бұрын

Full tutorial for the Quicksort algorithm in Java, with source!
Quicksort is widely considered the best sorting algorithm out there, but it can be very complicated to learn.
We'll walk through the entire quick sort sorting algorithm step by step, then walk through coding the entire thing in Java.
Quicksort doesn't have to be so tough to learn!
Learn quicksort by watching the whole algorithm being described and coded.
Learn or improve your Java by watching it being coded live!
Hi, I'm John! I'm a Lead Java Software Engineer and I've been in the programming industry for more than a decade. I love sharing what I've learned over the years in a way that's understandable for all levels of Java learners.
Let me know what else you'd like to see!
Source here: www.codepile.net/pile/X6lXog6G
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Пікірлер: 293

@CodingWithJohn 2 жыл бұрын

A few viewers have pointed out an issue where a value would be out of order in some situations. A couple of commenters, Wilson Barbosa and Yebo Qin, identified what the issue was and implemented fixes and noted them in comments below. I've included Wilson's fix in the linked code, so now it should all be working properly. Let me know if anyone notices anything else though. Thanks so much to everyone who saw this and proposed fixes! This community is clearly awesome. Also, this is why code reviews are a great idea!

@wbarbosabr 2 жыл бұрын

You're welcome, John! And keep up the good work!

@yeboqin5892 2 жыл бұрын

no probs, you ve done a great job !

@TuanBuianonymous 2 жыл бұрын

@@yeboqin5892 which case is it? please give me example

@duytuannguyen8323 2 жыл бұрын

@@TuanBuianonymous 15:49, line 43. There's an edge case. It's not absolutely the pivot will smaller than the left pointer.

@goldfish-bloopbloop Жыл бұрын

@@duytuannguyen8323 thank you so much!

@ginom219 2 жыл бұрын

Prepping for a coding interview in Java and I’ve gotta say, your videos are the best and easiest to follow that I’ve come across. Keep up the good work

@captainjacksparrow1328 2 жыл бұрын

Hey, how was interview? I hope you got a job

@PhilStein721 5 күн бұрын

I agree!

@MrDarshD 2 жыл бұрын

Well explained with the array visualization and the actual code creation process. Highly appreciate your time and efforts, John! Thank you so much!

@emekaukwuoma9507 2 жыл бұрын

Thank you John, you have just taught me quick sort algorithm in a way that is clear and understandable. I enjoyed watching and learning from your videos.

@Dalcenn 2 жыл бұрын

Seeing you explain this with the visuals made this so much more understandable than watching my professor do it on a chalkboard! Thank you for this explanation and the sample code. Another great video John.

@morhakak1907 2 жыл бұрын

Hi John, Your explanation was crystal clear + the last tweaks - the best quick sort tutorial on youtube right now.

@mindofpaul9543 2 жыл бұрын

Dude, You are so good at explaining these things! Thank you for making these more complicated parts of coding easier to understand for a novice like me!

@luanakimley2367 2 жыл бұрын

Thank you for these videos, they're the clearest I've found so far! Hope you keep making more 😄👍

@shwimwhearz4819 2 жыл бұрын

Instant sub, no one breaks down theses concepts quite like you John. Glad a found this channel

@ralfiasz 2 жыл бұрын

Definitely the best there is. Talking about your content obviously. You’ve helped me so much I couldn’t possibly thank you enough Sir!

@muhammadmuaaz3704 2 жыл бұрын

The explaination using the numbers was amazing bro I literally understoop every single word.

@wiilwaal258 Жыл бұрын

I dont know how i can thank u.. It took me yrs and never understood quicksort .. With ur tutorials i understood everything clearly. Thanks man 🥰

@YerushalayimShelZahv 2 жыл бұрын

Big thank you for sharing and teaching. I wish you much success with your channel and hope you continue producing more content. I look forward to your videos!

@codewithbug 2 ай бұрын

thank you, man. this is my fourth quick sort video and none of them are doing coding part. thank you, really.

@mockingbird3809 Жыл бұрын

This is honestly the best explanation on entire KZfaq!

@lindascoon4652 2 жыл бұрын

WOW, you have the talent of teacher. Thank you for making these videos.

@namrathas5804 Жыл бұрын

Thank you so much John, your videos are really a blessing to us. Its so easy to understand bcz of the visualization you make while explaining. thanks for your effort.

@siomarapantarotto 2 жыл бұрын

Thanks so much, John! I loved the way you explained QuickSort. 😍

@jeffreyslominsky7656 2 жыл бұрын

Your teaching is brilliant John, thank you for sharing!

@IsaacCode95 Жыл бұрын

great stuff! i really like your videos and the way you explain stuff!, i still had to rewatch this a second time to understand the code behind it, thank you!

@jondevlin4754 11 ай бұрын

Just watched two of your videos … have taught gifted grade 12 CS for years … now switching from C/C++ to Java …have just watched a couple of your videos … your communication is exemplary…so clear …

@kannanbalasubramani5541 Жыл бұрын

I wasn't this clear of quick sort before watching this one.. It helped a lot. thank you!

@carlostitlan Жыл бұрын

I only knew quicksort is the fastest. Now I know how it works and how to code it. I also practiced recursion. Thank you very much.

@RK-zg9cd 2 жыл бұрын

Thank you very much, John! I tried to find out working quicksort algorythm for Java, but the only one I found out has big bug. But thanks to you I won't be dropped out of my university))

@yavuzaydn6410 2 жыл бұрын

The explanation was amazing. Thank you John

@vladimirgorlin7510 2 жыл бұрын

It worths to mention that quicksort algoritm has in avarage O(nlog (n)) time complexity

@millerlou7294 2 жыл бұрын

This video will only 30k+ views explains the concept clearer than all other more popular videos, this guys deserves more subs!

@jugalsingh5176 2 жыл бұрын

Thank you for making us learn Java clearly and understand deeply😊

@SatyaMantha Жыл бұрын

This is the best QuickSort Algo I have seen in KZfaq

@Garrison86 2 жыл бұрын

Awesome explanation! really appreciate the time taken to make these videos.

@quitchiboo 2 жыл бұрын

Honestly the best tutorial on quicksort out there! I'd like to add: You don't have to use a number from the array as a pivot. You can calculate the median of the array and use that as the pivot, to queeze out even a little more performance.

@TuanBuianonymous 2 жыл бұрын

how to calculate the median of the array?

@quitchiboo 2 жыл бұрын

@@TuanBuianonymous Count how many numbers you have. If you have an odd number, divide by 2 and round up to get the position of the median number. If you have an even number, divide by 2. Go to the number in that position and average it with the number in the next higher position to get the median.

@thanhtungtran8249 2 жыл бұрын

@@quitchiboo in an unsorted array, the median could be any number, such as the highest or lowest number, so it does not make the algorithm that much better

@ShermukhammadKarimov 27 күн бұрын

as i found about this channel, when i search for programming related content, i pray that John made a video for that topic, and when he did, I got very happy.

@DarkLightning96 2 жыл бұрын

Great video, one of the best explanations of quicksort I've come across! It could've been better if at the end you compared quicksort with other sorting algorithms just to see the difference in the time it takes to sort arrays as they grow larger. Maybe you could do that in another video :)

@Joshua-te1fg 2 жыл бұрын

This tutorials tips like over loading and eclipse method maker gave me so much joy

@fredericoamigo Жыл бұрын

Thank you so much for this (and all of your other vids). You truly have an extraordinary ability to explain difficult things in an understandable and nicely communicated way. I simply love your vids! Keep up the good work!

@CodingWithJohn Жыл бұрын

Thanks for the very kind words!

@narendrakumariitb 2 жыл бұрын

Thank you so much John💚. What a great teacher you are 👏

@AndrewLapteff Жыл бұрын

BEST tutor about quicksort in universe!!!

@user-ci5gj9ks8o 11 ай бұрын

You're literally the best, thank you! Eagerly looking forward for new videos from you🤓

@mabeleain3320 Жыл бұрын

Thank you so much John. Best explanation I've ever seen.

@MTB_Bay_Area Жыл бұрын

Thank you, it is helpful that you show how it is done on a text file and you are moving the numbers in the text boxes. it is good visualization of the process.

@RAWRIHATEYOU1 Жыл бұрын

thank you so much John! I was getting really frustrated with myself because I've watched 3 quicksort tutorials, and the last video the comments were like "if you dont get it, you dont get it." felt really defeated but now I think I understand!! im currently a software engineer in test but I'd like to prepare for my future possibly as a swe. one of the videos I watched was choosing a pivot randomly in the array which had me like 🥴but this makes a lot more sense to me! kind of reminds me of binary search.

@ikennanana Жыл бұрын

Thank you so much for this video! You've really helped me get a grapsp on the QuickSort algorithm other than my professors over here...

@pinkymartini 2 жыл бұрын

Oh man you are amazing. Clear explanation. You have rightfully earned a sub sir.

@codeloners6820 2 жыл бұрын

very understandable! you are amazing tutor! keep doing such a wonderful video!

@adeyinkaolurin 2 жыл бұрын

Thank you John. Your explanation is very understandable...

@jaecheokkim99 2 жыл бұрын

Very easy and clear explaination! Thank you so much.

@abdurrouf4159 2 жыл бұрын

Damn. Your presentation is too smart. I really fall in love on your teaching approch. I knew how the quicksort works. But, couldn't able to make understand others properly how this sorting algorithm works. You demostrated these things nicely.

@adhamkhaled5399 3 ай бұрын

Wow, just amazing!! Thank you so much.

@thedevbek Жыл бұрын

@Coding with John, You did a great job on this tutorial. Thank you very much.

@nehemie_n Жыл бұрын

Clear and understandable way! Smooth and smart!

@hallosf1396 2 жыл бұрын

We're waitin for Heap Sort !! And thanks for your effort

@maryamz215 6 ай бұрын

First time i actually understood this algorithm. thank you

@francksgenlecroyant 2 жыл бұрын

You're amazing John, i am your new subscriber! I'm enjoying your content

@yaweno9555 Жыл бұрын

Very well done video on quicksort with Java. I'm impressed with John as an instructor from this first video of his I watched. John explains things in a way that is easy to digest and comprehend. I came upon this one after a demo of quicksort in a Learn Haskell video. This review helped me better understand some of that foreign syntax in Haskell. I do have to say that Haskell does the quicksort in far fewer lines than Java.

@sarkaholendova9080 Жыл бұрын

You have helped me get through University. I appreciate you so much! :)

@kesarscorpio 2 жыл бұрын

pointing the pointers points a pointing image in my head :D thanks for the explanation, very useful.

@sibrimbarcenasreales5525 3 ай бұрын

You are a really good master, thanks i think this could took me weeks to understand it well, but you made it so easy !

@kymberlicodes 2 жыл бұрын

This was so helpful! Thank you so much.

@funkyjunky845 3 ай бұрын

Yeah, that's a tutorial I was looking for!

@ntc3337 2 жыл бұрын

This is great thanks! I've 4 years working experience but I'm studying for job interviews and I always find myself having to go back and learn DS&A stuff haha

@ishank7239 Жыл бұрын

When I watched this video for the first time, I was a bit hesitant to implement it this way. It was because of the nested "while" loops. It took some careful observation to understand that although there are inner while loops, we only go through the array once : O(n) Thanks for this clear explanation. 🙏🏽

@timurboltaev8688 Жыл бұрын

Thank you, John. Great explanation.

@stephanieezat-panah7750 2 ай бұрын

Awesome tutorial. thank you!

@_Anna_Nass_ 2 жыл бұрын

Wish I had found this channel earlier. Great explanation once again, thanks!

@InvinciRD 10 ай бұрын

agreed 100%

@amandapanda3750 8 ай бұрын

Really Appreciate these videos ☺

@liatsahi 28 күн бұрын

Thank you for this explanation. thanks to you I understood brilliantly

@emerson3070 2 жыл бұрын

Needs a few re-watching lol Thanks John!

@K.K.M.DEALWIS Ай бұрын

your explanations are amazing

@odaia.7519 2 жыл бұрын

Wow that is so advanced and i understod, liked it. Thank you so much, hopfully one day would be able to create something like this after finishing my Study soon in 2 monthes

@kermitaner Жыл бұрын

This explanation of the quicksort algo is the best i've seen so far on YT. Maybe i try to implement it in Cobol on our mainframe next week, just for fun :- )

@amarsarkar4925 2 жыл бұрын

Was waiting for this ❤

@phekev 2 жыл бұрын

Me too. I'd recently watched the merge sort video and wanted a quicksort to compare it with.

@schwaccc301 Жыл бұрын

Best ever,! Thank you so much for sharing this!

@eugeniatatarchuk9641 Жыл бұрын

Thank you so much for your video! Everything is clear :)

@samuelevans9115 5 ай бұрын

your videos are amazing!

@kiranmayiippili6058 Жыл бұрын

You are too good. Wonderful explanation. Thank you tons.

@heartoutloud7498 2 жыл бұрын

Damn John. Im loving your videos man. You really clarify stuff which other tutors just ignore, that creates a lot of trouble. I actually would ask you if you could clarify the concept of returning. Plays a crucial role in coding and I miss the point of returning ometimes: "Does return close a program?" What is the point of returning is the return is void? " "Why do we have to return?" Thank for the great videos!

@checkmate2625 2 жыл бұрын

Hey man, Data structures and algorithms will become an interesting topic if everyone teaches like you.👍👍

@adokat 2 жыл бұрын

Extremely helpful, thanks.

@AbdurahmonMirobidov Жыл бұрын

just mind blowing , well done

@svalyavasvalyava9867 2 жыл бұрын

Your videos are educative and really fun to watch. Thanks for all the effort you put into the content!!! P.S. on 8:16 the rightPointer should point to the pivot element. However, your implementation was perfectly correct so this is not a big deal.

@CodingWithJohn 2 жыл бұрын

Thanks! And you're right, I suppose that is off by one between the implementation and the demo there. The end result should be the same either way.

@__nitinkumar__ 2 жыл бұрын

Thanks for that, I was implementing and had written the logic as int right = end -1; but in the John's implementation I saw it being as int right = end; // was a little confused here.

@abhishekkmr549 2 жыл бұрын

Your channel is true gem..

@anupamjoshi6077 2 жыл бұрын

Thank you so very much for helping me understand the concept as well as the implementation

@anupamjoshi6077 2 жыл бұрын

Also can we reduce one extra swap inside the while by surrounding it with an if condition which says that left pointer is not equal to right pointer

@KoushickSudharsanam 2 ай бұрын

Thank you man. you are the best.

@scottyp02 2 жыл бұрын

Great video!! Super informative

@shahdadpeykani7641 8 ай бұрын

Thank you sir, finally I could understand completely after watching 10 times 😂❤️

@Urbaez22 Жыл бұрын

Excellent video and explanation. I just add that when facing a StackOverflowError in Java, you can adjust the -Xss parameter to the JVM when booting up, to a larger value. By default I think it's 1024KB but can be set to whatever value necessary.. Thank you for your content..

@zeuss_2122 2 жыл бұрын

Thanks alot. My request was answered.

@dondigidon1633 Жыл бұрын

Really like your channel! Keep going, your are the best!🏆🏆🏆👍

@santoshpalli4432 2 жыл бұрын

Great explanation Sir, Thank you so much..

@wbarbosabr 2 жыл бұрын

I think I figured out what's wrong: When the chosen pivot is the highest number it'll end up in the wrong position when swapped from highIndex position to leftPointer position in line 61 of the code provided as in 2022-JAN-17. I solved this by substituting the said line for the following code... Suggestions for prettier, faster solutions are welcome! if(array[leftPointer] > array[highIndex]) { swap(array, leftPointer, highIndex); } else { leftPointer = highIndex; }

@CodingWithJohn 2 жыл бұрын

Great catch, I think you're exactly right! I put in that change and ran a number of tests, and it seems to fix the issue where that last value could be out of order. I've updated the linked code with your change, and will add a pinned comment about what the issue was (and give you credit of course). Thanks for checking it out!

@__nitinkumar__ 2 жыл бұрын

Hey Wilson, Correct me if I am wrong. From the fix I understood that, it is only required if you are taking the pivot randomly. Else there is no need of it. One suggestion would be from the readability point of view: _array[highIndex]_ is nothing but the _pivot_ variable so why not use that. :)

@wbarbosabr 2 жыл бұрын

@@__nitinkumar__ Yeah. In fact, you can just return highIndex at that point instead of assigning it to leftPointer and then return it.

@TuanBuianonymous 2 жыл бұрын

in this video, int rightPointer = highIndex => so that's why no need to check if(array[leftPointer] > array[highIndex]) . But in the source code rightPointer start from (highIndex - 1) so need check if(array[leftPointer] > array[highIndex]).

@andrescastaneda1208 2 жыл бұрын

@@TuanBuianonymous Agreed. I was just about to point this out. I prefer to just start the right pointer at the high index so there's no need for this logic check. Seems cleaner.

@elmehditalbi8972 2 жыл бұрын

Hello, John. Very detailed video! Thank you so much. Can you please do a video on generics in java as well ?

@coordinator3039 2 жыл бұрын

I really needed this for my Pokemon practice code project

@rasa7778 10 ай бұрын

Thank you very, very much for your videos, they are very helpful for me. You are doing a great Job. ♥♥♥

@RobinsonMartinezEngineer Жыл бұрын

You are the best!

@Palartzski 2 жыл бұрын

Great tutorial, clearly explained one of the more complex sorting algos!

@interstellarguy Жыл бұрын

Thank you John

@3042640426 Жыл бұрын

YOU SAVE MY DAY!!!!!!

@jonathancabral8124 Жыл бұрын

I was having difficulty to understand the logic behind the implementation and your explanation it’s really great. There is just one thing that I do not fully understand that is why choose a random pivot it’s better than always take the last or first element.