Dr. Rob Edwards from San Diego State University quixotically characterizes the quick sort algorithm, really the only sort you need or use.
Пікірлер: 183
@LeoUfimtsev6 жыл бұрын
I've watched about 6 videos on Quicksort. This one is really the best because it first explains the theory and then the in-place algorithm, where as most other videos only explain one or the other but algorithm is confusing if you don't understand the theory behind it. Thank you for this post. The reversed on-glass writing is kinda cool as well. Kudos.
@lucasv4q6 жыл бұрын
agreed!!! holy god this is mind blowin. great work sir!!
@kosiak108515 жыл бұрын
Did you really believe that he was writing inverse? And His left-hand writing is just coincidense then? Don't be naive! The video is mirrored obviously!
@Raminder553 жыл бұрын
Can you please help me with Sorting a Singly Linked List using Quick Sort. Please whatapp me if you can help me +919041121318 or mail me at mann.ramin@gmail.com. Thanks In advance..
@rosali75513 жыл бұрын
exactly!!
@benid31636 жыл бұрын
Wow. This should be the #1 search result for quicksort in KZbin. Understood it, and am now going to code it!
@enriquejaimes33685 жыл бұрын
Beni D agree, all others are very confusing.
@piyushsharma16386 жыл бұрын
teaching style is awesome.
@hackpiece30944 жыл бұрын
The only Quicksort vid that was Quick to understand ❤️
@imlijunglalongchar18585 жыл бұрын
I just spend the first 2 mins trying to figure out how they filmed it XD
@benzeltser98514 жыл бұрын
probaly a transparent wall and mirorred video by edit
@manuelfideles94684 жыл бұрын
it's called learning glass, it reverses the image in real time. No editing whatsoever
@minar75554 жыл бұрын
@@manuelfideles9468 no, the learning glass aka Lightboard does not reverse the image in real time. "...The lecturer writes on the glass surface with fluorescent markers while the session is recorded...Because any written text will be backward in the direct camera view, the text orientation must be flipped, either by pointing the camera toward a mirror reflecting the Lightboard and the presenter or by digitally reversing the image..."
@errorgrisha3 жыл бұрын
First time I was same )
@nakulankurmullam29823 жыл бұрын
Glass wall and video mirroring Edit: spelling
@abc170344 жыл бұрын
Am I the only one who is impressed not only with his algorithmic interpretation, but also with his digital whiteboard
@oo-gr2sw2 жыл бұрын
I think he uses translucent/noctilucent board markers.
@markdanskin82022 жыл бұрын
I feel like I watched 10 other videos and read a few articles about this but this finally got it through my head properly. This is really something that needs to be explained just like this to understand. I was getting far to bogged down with the recursion element to fully grasp the simplicity of this algorithm. This is a great explanation because it really just boils it down to what is actually happening, and the logic. Rather than getting encumbered by the actual implementation in a particular language.
@Revelatus6 жыл бұрын
swop
@FredoCorleone5 жыл бұрын
It seems correct even though it sounds weird
@LudwigvanBeethoven25 жыл бұрын
Its an optimized version of swap. Performs at least 10 times faster
@abhishekdas29304 жыл бұрын
He is British.
@tyrt400z3 жыл бұрын
I was like "why is he making fun of how he says swap" and then it hit 6:29 and I understood what you were referring to XD
@jayaprakash19512 жыл бұрын
Bro you are the best ! Man literally watched 7 videos to understand this method but your video is the one to understand this method
@jiageng19976 жыл бұрын
Amazingly done... my own lecturer left me more confused than before when he spoke about it
@Nikki-vg2pu6 жыл бұрын
Best explanation I've found so far!
@tsukikage4 жыл бұрын
This guy is creepily good at writing backwards...
@jrhager843 жыл бұрын
I hope you're kidding. lol
@tsukikage3 жыл бұрын
@@jrhager84 No? Am I missing something?
@tsukikage3 жыл бұрын
Oh, did they just mirror the video?
@jrhager843 жыл бұрын
@@tsukikage bingo
@ponka1285 жыл бұрын
One of the best explanations of Quick Sort. Thank you !
@tannerbarcelos68803 жыл бұрын
Clear. Concise. To the point. Will take a few watches but it was so clear and made so much more sense than what was taught in my algorithms class at school , lol.
@linlinli24402 жыл бұрын
thank you, this is the best quick sort i have seen, thanks.
@guygreenleaf4 жыл бұрын
These videos have helped me through my data structures courses IMMENSELY.
@BigMarini5 жыл бұрын
I'm Studying here in Sandiego SouthWestern College, Dr. Edwards you inspire me to transfer over SDSU to finish my Computer Science degree
@FLYAEROBOY6 жыл бұрын
Wow. Best Quick sort explanation. Deserves more views
@ramonaichim5150 Жыл бұрын
THE BEST EXPLICATION FOR QUICKSORT!! THANKS
@krisshore29175 жыл бұрын
I finally understood after watching this and was able to implement the algorithm. Thank You!
@pacodinorin45773 жыл бұрын
This was the best way to learn it, I'm Mexican and my teacher is so bad, thanks to you teacher Rob
@ythien71475 жыл бұрын
Thanks Dr.Edward This video is really clear. I had a hard time in class to understand this.
@sudajared3 жыл бұрын
Best explanation of quicksort I have found so far
@acemccrae78626 жыл бұрын
Thank you, been trying to understand this for 4 videos including my instructor. Good Job.
@ujtelomvan04145 жыл бұрын
All the videos are different. Wtf? Now what?
@__kpsingh__4 жыл бұрын
This should be at the top of the search list.
@RicardoBuquet2 жыл бұрын
This is the best explanation I have seen so far.
@SageofToads6 жыл бұрын
Best quicksort video ive seen.
@singsarav4 жыл бұрын
Excellent method of teaching. Every one can easily understand
@omarabdelkader52148 ай бұрын
Thank u for ur great explanation, got it from the very first time
@raymonddevries53414 жыл бұрын
Best explanation of quick sort I have found! Thank you.
@twerkyfingers3 жыл бұрын
This is the best video on quick sort!
@FredoCorleone5 жыл бұрын
This guy is awesome, I'm learning sorting algorithms thanks to him. One day baby I'll be sorting integers at Microsoft! _function quickSort(array) {_ _if (array.length
@mandolinic5 жыл бұрын
In practice, the number of times you ever need to sort a list of pure numbers is small. It's far more common that you need to sort some structured data, where there's some item within the structure that is the sort key. When I started programming 40 years ago, it was reasonably common to hand code a sorting algorithm for some application, now every modern language comes with a Quick sort algorithm that you no longer need to worry about. How it works is of purely academic rather than practical interest.
@igori11784 жыл бұрын
Thank you so much for your videos. You have a talent to explain things in easy way!
@zheyuanliu48813 жыл бұрын
Thank you professor!! This is really clear and understandable, I now understand how partition work and how it works with pivot point.
@christopherward72326 жыл бұрын
This was a great video! Actually managed to follow through your method and stopping to code each step that you explained. Thanks :)
@tamborelconejo3 жыл бұрын
best explanation I saw so far
@bzavolovich2 жыл бұрын
Thank you for this wonderful explanation!
@majuran4 жыл бұрын
Best video...... finally understood the concept... thanks sir
@seankalbak5446 жыл бұрын
Well done and nice job with the reverse writing. That made the video really viewer friendly.
@jakubfraczek1208 Жыл бұрын
Very good explanation! Thank you very much :D
@akruijff2 жыл бұрын
8:50 yes, but if the list is sorted, then the middle is better.
@madhatshahda4179 Жыл бұрын
really great work . It felt like listening to the John Danaher of sorting xD
@MegaRc19896 жыл бұрын
how are you writing backwards!?
@yasahanzengin33296 жыл бұрын
He's writing on a glass.
@phillippebr6 жыл бұрын
They are filming a mirror. He is writing normally in a glass (so everything is backward) and they are filming a mirror pointed to it (making it forward again).
@hussainm84076 жыл бұрын
or theyre just flipping the video in post
@FlamAble945 жыл бұрын
@@hussainm8407 BAHAHA xD
@mahmoudnadi19925 жыл бұрын
sorcery
@johnyhawkahsan6 жыл бұрын
Awesome! Very short and to the point.
@slippinchillin2 жыл бұрын
I would give 10 likes if I can for this video! Very well explained! Thank you!
@isaacdouglas11194 жыл бұрын
3:41 wouldn't you have to quicksort one more time since it's not guaranteed at that point that the remaining list is sorted? The list could still be [12, 11] instead of [12, 14] at that point.
@RickAstley19884 жыл бұрын
That's the only problem in quick sorting, but it happens rarely that's why quick sort is being used mostly
@isaacdouglas11194 жыл бұрын
Kurt Weyne Gaso don’t think that’s a problem with the algorithm itself they just forget the last iteration
@sinify66763 жыл бұрын
@@RickAstley1988 i don't think people use "sorting algorithms" with small chances to just return unsorted data..
@sanjeevkumarsen48383 жыл бұрын
Superb explanation 🙏🙏
@nikomiller61683 жыл бұрын
Using the last element as a pivot is necessarily not a good option if there is even a slight chance that the list could be (nearly) sorted. A good option for pivot selection is the median-of-three method in which you choose the median of the first, middle and last element of the list as your pivot. This leads to efficient behaviour for all inputs.
@tahirmahmood17214 жыл бұрын
Describe precisely the pivot step of QuickSort, using the median-of-three method for pivot selection, and show every stage of the rst pivot step applied to the array with the following entries: 3; 4; 7; 1; 2; 6; 5
@connorjones68966 жыл бұрын
Thankyou! you made this concept easy to grasp
@jidejaydee3 жыл бұрын
am too lazy in writing a comment but this tutorial made me do that! THANKSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS
@redtree7323 ай бұрын
Best explanation
@MuntahaZad4 жыл бұрын
Thanks a lot! Also for no annoying music!
@reynaldoruizflores3 жыл бұрын
How can we exactly count the number of comparisons? I establish a counter for 10000 number am I obtain 9999. If I consider the recursion -1 each time the numbers goes to 12K. Depending of the start or end or media election differs too.
@JoffreyB6 жыл бұрын
but what about array of |8|10|7|12| , out pivot is |12|, i and j counters in this case will go together until the end, coz all elements are smaller than pivot. And in the end we should switch |7| with |12|, isn't it? but we will get then |8|10|12|7| , which is far from true. Somebody explain me please this moment
@noelthomasbejoy30896 жыл бұрын
Watch the vid agin .we skip through the i(update it by 1) when element(i)>pivot.so swaps take place before pivot and element(j )swap.
@mrmrigank71545 жыл бұрын
Actually in that case counter who is remembering current posn will remain at 8 and other counter which is finding 1st element greater than 12 will iterate and end the array nothing will happen. And in next step you will send arr 8 10 7 in recursion and 12 in recursion
@911wildman9115 жыл бұрын
I believe I've found an answer here, having encountered the same confusion when reviewing this myself. When you have this scenario, you simply do not perform a swap at the end. The final value before the pivot value is considered to be in its "sorted" position. From there you can mark the final value sorted and continue the process with a new pivot.
@travel_with_dimpi5 жыл бұрын
Great explaination and u r sophisticated person
@ruicsf3 жыл бұрын
Thank you!
@xiaofan91023 жыл бұрын
beautiful explanation!
@sandyjust3 жыл бұрын
So the swapping of 6 and 8 is not required. Just use the last element in the list. I think this is the inplace quick sort using Lomuto partition schema.
@vishal240003 жыл бұрын
'crystal' clear.
@prabhakarpalanivel64725 жыл бұрын
Thanks. Notes: Partition algorithm at around 5:00
@8971felix5 жыл бұрын
Excellent explanation
@number1neek3 жыл бұрын
The comments here: 🤯 I was much more amazed by how he was able to disappear and then reappear in almost the same place! Then I realised, this must be what recursion is... I am learning!
@jaroslawpiwar58112 жыл бұрын
Geniusz dydaktyczny. Brawo.
@cornevantonder74396 жыл бұрын
I have been through video after video, website after website and NONE of them were able to help me understand quicksort. Within the first 2 minutes of this video it all made sense. THANK YOU!!!
@foodandmoney5 жыл бұрын
Excellent explanation.
@KA-jb4qv3 жыл бұрын
how come the video was captured?.. he seemed writing in air, and he is facing opposite to us
@Jagadishkumar46464 жыл бұрын
First value is taken j last value is pivot is taken if first value j is less then pivot what we do and i is taking increment to the j
@ИльяЛагойда6 жыл бұрын
Very good lessons. Thank you!!!
@sathwikchintalapudi12434 жыл бұрын
Nice video thanks
@short_cut_hub4 жыл бұрын
Thank you sir Great work😊
@JoffreyB6 жыл бұрын
i can't get, what is the second part about?
@chandramohannegi6 жыл бұрын
best quick sort thanks
@hujake54064 жыл бұрын
THANK YOU SIR
@jonathansimons23686 жыл бұрын
is he implying that the middle number of an unsorted list is better than any other as a pivot choice as it is likely to be nearer the median than the others?
@abdellatifsraiti20324 жыл бұрын
THANK YOU
@chigoziea.9915 жыл бұрын
I do have to say this algorithm is just slightly different than some other youtube videos :P. Great video!
@Sgoose1054 жыл бұрын
The sound made between the pen and the glass...
@Maen9634 жыл бұрын
BEST OF THE BEST !
@MasonAulsbrook Жыл бұрын
Seems a lot easier to just do a normal sort smallest to largest. Don't understand the reason for the complexity.
@fireflies155 жыл бұрын
good one. thanks a lot
@nishanthkr28383 жыл бұрын
What sorcery is this
@bobhutchinson36384 жыл бұрын
The partitioning algorithm is not optimal. If an array is in descending order the swap would do unnecessary job.
@911wildman9115 жыл бұрын
Something does not appear to be correct here or maybe I am misunderstanding. With the 8, 10, 7, 12 sort you would do if you had continued this example, all the elements are less than the pivot (12). Your blue/orange counters would stay together until the end, resulting in a swap of 7 and 12, resulting in 8, 10, 12, 7. This is not correct. Is there some gotcha or small detail here that I am missing in which the result would come out correct? Thanks!
@bobhutchinson36384 жыл бұрын
>resulting in a swap of 7 and 12 You would end up with swapping (12 with 12) nothing BUT! You would have a new pivot winch is 3(12). End the next iteration would be: leftSort(0, 3 - 1), rightSort(3 + 1, 3)
@tirupatirao75214 жыл бұрын
Darkmode teaching 👌👌😉
@knightyang15616 жыл бұрын
I still don't understand why choose the middle number as pivot point and then swap it with the end number in the almost sort list? Am I miss something?
@icosmini5 жыл бұрын
That is confusing, he shouldn't have said that. You actually simply choose the last number as pivot. And you do that so that you can freely move all the other numbers around. And then at the very end, when you have the set of small numbers and the set of large numbers, you put the pivot between the two sets.
@mrmrigank71545 жыл бұрын
@@icosmini it is not confusing actually you can chose any number as a pivot, then have to swap it with the last one ,, choosing last one as a pivot is convenient . pivot means here that you have to place this element at its right place and left elements must be smaller and right must be bigger
@mrmrigank71545 жыл бұрын
right place means where it should be .
@ahmidahmid93035 жыл бұрын
that will help alot if you sorting nearly sorted set where there will be less swaps mostly if you use the mid number
@huynhat505 жыл бұрын
middle is for the meaning, the last is for the implementation
@va9if2 жыл бұрын
dat breathing
@ajai.a23746 жыл бұрын
thank you
@x9466x4 жыл бұрын
*s w o p*
@amphivalo7 жыл бұрын
Thanks
@akshaysapkale27896 жыл бұрын
Dyslexia 🤔🙍 But anyway it was fun and very helpful for me
@ianpoulsen56233 жыл бұрын
am i going crazy or did he just say 10 is less than 7
@ArjunPatel-hi5eq5 жыл бұрын
LOL WOW IS HE WRITING BACKWARDS?
@oscarwang79204 жыл бұрын
great video but the list is not sorted lol 9:00
@xoxoo48776 жыл бұрын
Great
@sty16237 ай бұрын
Its called quick sort but its not the quickest
@theanonymoustalk5 жыл бұрын
"swop"
@zbynekjuros51395 жыл бұрын
Unacceptable 4:10 !!
@kosmickarma296 жыл бұрын
How the hell you write in mirror image!!??@#£_
@swolebastard5316 жыл бұрын
Either the guy is brilliant or they mirrored the video afterwards...
@kosmickarma296 жыл бұрын
Yeah....actually I searched about this on the internet...there is something called lightroom...They do mirror the video afterwords....