Quick sort in 4 minutes 

Yeah, in the early days I didn't spend enough time on pseudocode. Trying to fix that now by building out this repo: github.com/msambol/youtube/blob/master/sort/quick_sort.py. Thanks for the feedback!

​@@MichaelSambol I got really confused when the pseudocode didn't match the explanation. You should correct that (in the video) ASAP.

@@westsideslasha I'm sorry about that! RU-vid won't let me change the video now unfortunately, but I pinned this comment.

I am encountering an infinite loop if I change the while condition to be i < j instead of

i am glad that i looked at the comment section after having a hard time connecting the pesudo code to the video content.

same lol all the quicksort videos use the same words to explain it

hey man, after pulling my hair out for 2 days I finally got it, sadly I had to pay for it.

@@user-wp9pz9hl3z what did u pay for?

@@HACKINGMADEFUN a Udemy course

@@user-wp9pz9hl3z cool

it gets halved and is recursively applied to both halves in each step

@@Evokans um what?

@@sleevman2307 It gets repeatedly done on each new half, as after each half the pivot is in the right place, so a new pivot is used.

@@faith2756 sorry wat?

@@sleevman2307 Which part exactly do you not understand?

understanding the meaning of pivot is the KEY.

yeah, theitemfromleft, or right wasn't even properly discussed, left of what or right of what exactly?

lol

You really should. *SAD!*

@@SkillUpMobileGaming You too

wait what. why

lol 😂😂😂

that's what I was thinking. you're a genius pal

HAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA

After you swap itemFromLeft and the pivot at the end, itemFromLeft is now at the end of the array. So, use that as the *new* pivot. Repeat that until its sorted.

@@airex12 so 8 is the new pivot? How can I go through if there is no number in the array greater than 8?

@@kennethquilantang8080 after 7 is put in its correct position, remember that all numbers to the right of 7 are greater than 7. In this case, there is only one number - 8. A partition with just one number is already sorted, so you can ignore it and move on to sort [6,5] to the left of 7. For sorting [6,5] choose 5 as the pivot. itemFromLeft is therefore 6, and itemFromRight has no value because no number in the array smaller than 5. Therefore, we can stop and swap itemFromLeft and the pivot to leave [5,6]. Yes, the video is unclear because it does not explain these cases. The point is that each time you put the pivot into it's correct position, you have "split" the array into two parts - one part has all numbers bigger than the pivot and the other part has all numbers smaller than the pivot. Parts with *just one* element are already sorted. If a part is already sorted, no itemFromLeft can be found. If a part is unsorted, you are guaranteed to find an itemFromLeft, and if the index of itemFromRight < the index of itemFromLeft *OR* itemFromRight does not exist then you can swap itemFromLeft and the pivot to put the pivot into its correct position in the whole array.

@@airex12 I get your point bro thanks but what would be the next step. Will I need to pick another pivot? How can I sort the rest?

haha, I can't help imaging Ross's face, hahaha

Me in future, oh Ross's couch sort?

screams in Chandler voice SHUT UP! SHUT UP! SHUT UP!

Oh my GOOOOD :-))))))))))))) So truuuuueeeeeee

This is exactly what came into my mind learning about this :))

I want more videos like this where they explain stuff in less than 10 minutes

Bet ? ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Zh37XyQLHkw.html

there's a video by abdul. i think it is best

Thats the fanciest wording I've heard, i would use: "You get it or you dont"

Try to sort a few short sequences yourself according to the steps in the video. You may get the "background knowledge".

I've been looking at it for a few minutes now, and I can believe that this pseudocode is accurate, but I'd have to check the details of what the partition function is doing to be sure, but it seems legit. Assuming your language of choice will permit a self-referential function like that.

@@diabl2master The recursion is fine... he's talking about how `partition` is putting the pivot on the left wall instead of the right. In the video the pivot is on the right side.

@@jscholex That would be a failure of technically reflecting, not intuitively reflecting, the walkthrough. I'm not sure OP was referring to that, but who knows.

@@diabl2master Yeah who knows... but I think we can all agree the pseudocode isn't great hah

the pseudocode shows the Lomuto version but the visualisation is for the Hoare version, which is better. See Wikipedia for both.

N Betancourt cuz the way he explains it IS confusing I’ve watched this a couple of times, thought I understood went to the exam and screwed up Now that I’ve watched other videos I understand that the way he explains it is confusing

N Betancourt He made it more confusing, for sure.

He didn't explain what quick sort does in general, what it can be applied to, and left some holes in the explanation that someone with no experience would struggle to grasp. Which is a shame.

Hope this helps :ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Zh37XyQLHkw.html

i hope you got it cute bird from nichijou

Well said 👍

Makes perfect sense to me

Christian May That’s so great! 🙌👏

I thought the visualisation was fine. I feel that I understand it now.

This is the fist visualisation of quick-sort I've ever seen, so I know it doesn't mean much, but I agree.

thats gonna b me td lmao

@@fireboywatergirl1625 i am sure you are at the right place.

Thanks for the explanation!

what the hell are you talking about this is a church sir

@@jamboy1843 I don't even remember making this comment.

Thank you. I feel the same about my actual online course I'm studying. And I'm a newcomer. I feel better.

horrible

pseudocode is actually wrong as well !

@@hiteshsahu_ Exactly, not only 1 pointer moves & stopping when this 1 pointer reaches end of the array, but also only picking leftmost value as pivot

@@hiteshsahu_ Exactly , i have wasted so much time over it

​@@blurryhorizon I suppose that in the Partition function, the "pivot = A[low]" should actually be "pivot = A[high]"? Very confusing so I wrote it down and found out that the pseudocode doesn't work properly. // Oh just realised that although pivot = A[low] might works as well but the pseudocode is totally wrong for Partition function jeez..

@@scarlettwang2146 I think it should be as it is. Something else is wrong.

yes! It is cool!

thank you a lot!

VERY UNIQUE TASTE 8|

Wtf

Lol

lol

@@zolongOne lol again

God bless, Mitch

You mean itemFromLeft and ItemFromRight? They can't be equal beause they were chosen to be greater and lower than the pivot

thank you

You don't swap the indices. You just change the numbers in the indices

Honestly the phrasing is confusing. This easier if you ignore half of it and just watch the numbers. Edit: ok, maybe bad advice..

@@thehammurabichode7994 indeed bad advice

but how could A[high] be less than pivot if the high is supposed to be a value greater than pivot? and why not always pick a pivot from the middle?