Time to time i find myself coming back to your videos, sometimes for revision, sometimes for just interest and I never leave unsatisfied. These videos although are free, but are of premium quality. Better than paid courses
14:30 As *n - k = 1*, then *k = n - 1*. Thereby, we will have a slightly different final result for this calculation: (n ^ 2 * c + n * c - 2 * c) / 2 + c1 Anyway, we conserve the fact that this algorithm takes n ^ 2 of cost in the worst case. Awesome video teacher! Super enjoyed!
2 days ago j learned about merge sort and quick sort , but at today morning I thought that I hadn't got the exact logic or idea to solve them , so I decided to learn from your channel and just completed and boom💥,I am satisfied with the explanation (deep explanation) tha k u for making such brilliant videos🔥❤️
I loved the way you explained all sorting algorithms and its analysis. If you can add heap sort and radix sort in this list, that would be very helpful. Thanks :)
I dont mean to be so off topic but does someone know a way to log back into an instagram account?? I somehow lost my login password. I would love any tricks you can give me.
@Joel Larry thanks so much for your reply. I found the site on google and Im in the hacking process now. I see it takes quite some time so I will get back to you later when my account password hopefully is recovered.
Please upload video lectures on hashing, heap sort, bucket sort and shell sort as well.. These videos have really proved very helpful in understanding sorting algos in a better way..
Teacher, at minute 17:06 we cannot forget of adding a return statement into RandomizedPartition as follows: RandomizedPartition(A, start, end) { pivotIndex
Amazing lectures and best way of describing things with programs and complexity analysis for every one. I am waiting for next sorting like heap,redix etc. Please please upload those too.
Nice video :) Really helped me... Just one thing though: RandomizedPartition() should return pIndex to QuickSort() call, so I think Partition() inside RandomizedPartition() should be called as "return Partition()" Thank s for making such hugely helpful videos, keep up the good work...
Please make an addition of Binary Search Algorithm and its analysis as it is also an important tutorial which follow Divide and Conquer Rule. Other than this you have every tutorial regarding Design and Analysis of Algorithm. P.S. YOU ARE AMAZING.
Thanks so much! Your videos are so great! I now look at your channel first if I need to review something. Just about broke my heart not to be able to find heap sort amongst the videos. Something to consider!
@@loveanimals-0197 UA-cam creators explaining topics not just in computer science but math and science are superior to outdated teaching methods of textbooks and many "professors"
+Piyush Jaiswal if u 'll put k=n-1 ,then also the complexity 'll come-O(n*n), SOLUTION- T(1)+(n-1)*c*n -(n-1)*(n-2)*c/2 c + c2(n*n - 5*n +2) cn*n-5*c*n+2 =O(n*n) Hope it explains...
At 18:24, either it should be summation from i=1 to n instead of i=0 to n, or if the limit is from i=0 to (n-1) then T(i) + T(n-i-1) should be written btw nice lecture.
Just wanted to say, amazingly explained. One query though, at 14:28, it is explained n-k = 1 , so k = n. This seems right? So either base case should T(0) or calculation will be made for k = n-1.
Annihilation condition for worst case, where you've written "n-k=1" is right, but further equated to 'k=n' is a mistake, "k=n-1" is correct. This might bring some difference in the final equation but complexity remains the same n.log(n)
What if we use the "median 3" value as a pivot? We get three values from the subarray: The first, last and middle elements. Then we check the 3 values and determine which one is in the middle. Let's say that the elements are 4, 9 and 1, the element in the middle is 4, and we use that as our pivot. Then, we can re-arrange the elements: 1, 4, and 9 before subdivide the array.
Yeah we can do that the median of 3 will have same complexity as the lomuto or the partition shown in the video ...but median of 3 will run faster it decreases some constants and also one could always use random pivot to not get the constant and settle in the average case...and I think we only have ways to prevent to get worst case for quicksort..I don't think we can somehow change the complexity of the worst case for the quicksort....For better time complexity one could always take 2 pivot points, as It is found more the pivot point the quick the quicksort will work but if one encounters worst case for quicksort the complexity would always be O(n^2)
I have a doubt , would that randomized qs be at all effective ? since eventually , we are just shifting that random value to the end , that is also a random value .
It doesn't matter where the pivot is placed. The value of the pivot matters. We are trying to avoid possibility of choosing the largest or smallest value in the array as the pivot, since that would lead to a skewed partitioning. By choosing the pivot randomly from the array, we are making sure that doesn't happen. Since choosing a non-extreme value is much more probable than choosing an extreme value, this approach is v effective. Shifting the pivot value to the end of the array just makes sure we can retain the same code we wrote if we just chose a pivot from the end :)
+mycodeschool can you please explain how the given program for quicksort is not stable??? I have tried to take examples but I am still not getting it??
mycodeschool your videos are amazing please can anyone explain me that how random no. is chosen as pivot.I understood that another function is made for this purpose but how will this function work?
i will have the same value only at first position . and then the first swap is just like swap(2,2)....which can be avoided with giving condition like if(i!=PIndex) swap(A[i],a[PIndex]);
What's wrong in my code int arr[]={4, 5, 6, 2, 1, 7, 10, 3, 8, 9}; int size=sizeof(arr)/sizeof(arr[0]); quickSort(arr, 0, size-1); void quickSort(int arr[], int low, int high) { if(low>=high) return; int partionIndex=randmized_partition(arr, low, high); quickSort(arr, low, partionIndex-1); quickSort(arr, partionIndex+1, high); } int partition_arr(int arr[], int low, int high) { int pivot=arr[high]; int partionIndex=low; for(int i=low;i
At each step n is being divided by 2 to get n/2, then n/4, then n/8 and so on. In general it is T(n/2^k) with k being the number of times we've done that division. (Try this out for different values of k if you find it confusing) We want to take that expression to the base case of T(1) at which point n/2^k = 1. Hope this helps.
Time to time i find myself coming back to your videos, sometimes for revision, sometimes for just interest and I never leave unsatisfied. These videos although are free, but are of premium quality. Better than paid courses
14:30
As *n - k = 1*, then *k = n - 1*.
Thereby, we will have a slightly different final result for this calculation:
(n ^ 2 * c + n * c - 2 * c) / 2 + c1
Anyway, we conserve the fact that this algorithm takes n ^ 2 of cost in the worst case.
Awesome video teacher!
Super enjoyed!
I noticed that too and your comment confirmed I'm not missing something. Thanks!
Incredible how your explanation made quicksort algorithm and its analysis so easy
17:53 if the pivot lies at index i, then there are i elements in the left partition and n-1-i elements in the right partition(In a 0-based indexing)
2 days ago j learned about merge sort and quick sort , but at today morning I thought that I hadn't got the exact logic or idea to solve them , so I decided to learn from your channel and just completed and boom💥,I am satisfied with the explanation (deep explanation) tha k u for making such brilliant videos🔥❤️
I should say your videos are the best in making the things simple and understandable. Please upload more videos
thank u sooo much we just did it in school .. and i wanted to revise it and here u are uploading the video of it
You're most welcome Mouad Izegnane :)
I loved the way you explained all sorting algorithms and its analysis. If you can add heap sort and radix sort in this list, that would be very helpful.
Thanks :)
I dont mean to be so off topic but does someone know a way to log back into an instagram account??
I somehow lost my login password. I would love any tricks you can give me.
@London Andres instablaster =)
@Joel Larry thanks so much for your reply. I found the site on google and Im in the hacking process now.
I see it takes quite some time so I will get back to you later when my account password hopefully is recovered.
@Joel Larry it did the trick and I finally got access to my account again. I'm so happy:D
Thanks so much you saved my account !
@London Andres No problem =)
Please upload video lectures on hashing, heap sort, bucket sort and shell sort as well.. These videos have really proved very helpful in understanding sorting algos in a better way..
Teacher, at minute 17:06 we cannot forget of adding a return statement into RandomizedPartition as follows:
RandomizedPartition(A, start, end)
{
pivotIndex
built more confidence in challenging google from your lectures, thx !
Thank you so much for this video!!! This has to be by far the most helpful CS programming learning video, that I have ever watched.
Amazing lectures and best way of describing things with programs and complexity analysis for every one. I am waiting for next sorting like heap,redix etc. Please please upload those too.
Amazing series. It took me less that 2 hours to revise what used to take days for me.. .Best Way of teaching.
very thanks, you are the best teacher for algorithmic on youtube
I'm addicted to your lessons... so after 4 years, are there still more?? :)
Im sorry but he passed away 6 years ago :( You can find about him here www.quora.com/Who-was-humblefool
@@aditya234567 the one who passed away is Harasha Suryanarayana(co-founder) and the voice youre listening on here is of Animesh Nayan
your videos are much better than those on coursera!
Nice video :) Really helped me...
Just one thing though: RandomizedPartition() should return pIndex to QuickSort() call, so I think Partition() inside RandomizedPartition() should be called as "return Partition()"
Thank s for making such hugely helpful videos, keep up the good work...
this channel is gold
this is great. thanks so much. couldn't understand a word of what the instructor at school said. you explained perfectly.
Superbly explained! Thank you for these videos. I have an algorithm interview, hope this helps.
where is link to description of all the maths mentioned at time 18:39
dat was bluff xD
It's not that hard to google with the term "randomized quick sort time complexity analysis"
look it up in cormen's book
It's forward recurrence(extremely easy stuff), computes the running time complexity.
Just search it.
Please make an addition of Binary Search Algorithm and its analysis as it is also an important tutorial which follow Divide and Conquer Rule. Other than this you have every tutorial regarding Design and Analysis of Algorithm.
P.S. YOU ARE AMAZING.
Thanks so much! Your videos are so great! I now look at your channel first if I need to review something. Just about broke my heart not to be able to find heap sort amongst the videos. Something to consider!
this person is god at teaching..
Please add further videos of all the playlists and thank you very much for the amazing, animation explanation. Love a.
you should do heap and radix sort
Those were not in the book he copied from.
@@loveanimals-0197 what book ?
i think he use algorithm in c by sedgwick
@@loveanimals-0197 he is not alive. He expired in some accident 4 years ago
@@loveanimals-0197 then go on Karen read books instead
@@loveanimals-0197 UA-cam creators explaining topics not just in computer science but math and science are superior to outdated teaching methods of textbooks and many "professors"
you are really very very good at explaining!
14:30
n-k = 1; k=n ( should be n-1 )
+Piyush Jaiswal
if u 'll put k=n-1 ,then also the complexity 'll come-O(n*n),
SOLUTION-
T(1)+(n-1)*c*n -(n-1)*(n-2)*c/2
c + c2(n*n - 5*n +2)
cn*n-5*c*n+2
=O(n*n)
Hope it explains...
maybe k and n are both much much larger so k approximately equals n
amazing lecture !! I feel much more clear about quicksort now.
Please in future lessons i hope you will make videos on radix sort and shell sort and thank you for these nuggets of programming lectures
BRILLIANT PLAYLIST THANK YOU!
At 18:24, either it should be summation from i=1 to n instead of i=0 to n, or if the limit is from i=0 to (n-1) then T(i) + T(n-i-1) should be written
btw nice lecture.
THANKYOU FOR DOING SORTING ALGORITHM VIDEOS...this helped me a lot
but sir please make video on heap and radix sort also
k will be equal to n or n-1?
n-1
+mycodeschool thanks for the video! Could you please post the link you are mentioning at 18:39 ?
You are purely gifted sir, love your lessons
Just wanted to say, amazingly explained. One query though,
at 14:28, it is explained n-k = 1 , so k = n.
This seems right? So either base case should T(0) or calculation will be made for k = n-1.
i think while finding time complexity in worst case ,for generic expression when n-k=1 then n=k+1 or k=n-1..
i think that too.. finally what's the deal here..? have you figure out..?
yea, that's truth, but it doesn't matter that much, because the greatest element in polynomial will still be n^2.
fair thought....but the twist is, for a very large value of n : n-1 -> n
just aweshome,great sir,come again on youtube sir
Annihilation condition for worst case, where you've written "n-k=1" is right, but further equated to 'k=n' is a mistake, "k=n-1" is correct. This might bring some difference in the final equation but complexity remains the same n.log(n)
Thanks a lot!!! It really help me to understand concept of all sorting algo very easily..
Thank you! A great explanation. I keep coming to your videos from time to time. lol
Good and clear Explanation.. Thank you..
Thank you for sharing such a great knowledge.
What if we use the "median 3" value as a pivot? We get three values from the subarray: The first, last and middle elements. Then we check the 3 values and determine which one is in the middle. Let's say that the elements are 4, 9 and 1, the element in the middle is 4, and we use that as our pivot. Then, we can re-arrange the elements: 1, 4, and 9 before subdivide the array.
Yeah we can do that the median of 3 will have same complexity as the lomuto or the partition shown in the video ...but median of 3 will run faster it decreases some constants and also one could always use random pivot to not get the constant and settle in the average case...and I think we only have ways to prevent to get worst case for quicksort..I don't think we can somehow change the complexity of the worst case for the quicksort....For better time complexity one could always take 2 pivot points, as It is found more the pivot point the quick the quicksort will work but if one encounters worst case for quicksort the complexity would always be O(n^2)
That was quick analysis of the quick-sort, ladies and gents.
thank you sir...these videos are really awesome.
but sir please make video on shell and heap sort.
you are great mathematician bro thanks
a big thanks to you sir....Great explanation.
thank u so much. it was really understandable. especially it gave me some confidence regarding code implementation.
great explanation 👍👍👌
Hey,
I just wanna tell u that u did great job ...
But I want u to cover up heap sort(imp) and other sorting algorithms as well.
Till date i just heard about randomized partition but didn't know now i got it
can u upload videos on heap sort and radix sort asap plz?? btsw excellent explanation..
your video is extremely good for understanding :D!!
please record more sorting algorithm :D
@mycodeschool: Could you please provide a link to the Average case mathematical analysis?
Thank you so much for very descriptive video on Quick sort. Please can you post a link for mathematical solution of T(n).
awesome video....nicely explained
Wow! What an awesome video! :D
8:22 Instead of a, I'll write c, because c looks good, when I am saying its a constant.... XD
Good stuff !!! Loved the font... Can u post what application you used for writing and capturing the video ?
Sabesan Saidapet Pachai blog.mycodeschool.com/2013/11/how-to-create-amycodeschool-style-video.html
14:31 why n-k=1 => k = n Can someone explain this to me ?
BEST VIDEO EVER
Great tutorial . Thanks
your videos are awesome !!
more algos plz ...
I have a doubt , would that randomized qs be at all effective ? since eventually , we are just shifting that random value to the end , that is also a random value .
It doesn't matter where the pivot is placed. The value of the pivot matters. We are trying to avoid possibility of choosing the largest or smallest value in the array as the pivot, since that would lead to a skewed partitioning. By choosing the pivot randomly from the array, we are making sure that doesn't happen. Since choosing a non-extreme value is much more probable than choosing an extreme value, this approach is v effective. Shifting the pivot value to the end of the array just makes sure we can retain the same code we wrote if we just chose a pivot from the end :)
+mycodeschool can you please explain how the given program for quicksort is not stable???
I have tried to take examples but I am still not getting it??
amazing videos thanks a lot
will you help me with radix and shell sort algorithms
Great, you helped me a lot. :)
What if we took the random index from 1 to n-2as it will then never choose the last and first element?
Can someone please explain me how he has done that math in 13:11
Very helpful!
thank you so much fr this tutorial.. bt plz can u help me with randomized quick sort time complexity calculations??
mycodeschool your videos are amazing
please can anyone explain me that how random no. is chosen as pivot.I understood that another function is made for this purpose but how will this function work?
+Yastika Kumar This won't be a function you write. Instead, you'll be using the language's random generator function. Just look that up.
At 14:53, shouldn't k = n-1?
Yes, it is a typo but for calculating Big-O notation it is still n-square (n^2) terms.
yes, it should be n-k=0, hence k=n
sir would you please give the link to time complexity analysis in randomized approach for the sort ?
Can you do the gravity sort next?
if the Array is {2,7,1,6,8,5,3,4} then how will it work-> 'Pindex' and 'i' will have same values all through the loop
Please help
pindex will be incremented only if a[i] will be smaller than the pivot element i.e 4 in your case whereas i will be incremented after every element.
No it will not.
i will have the same value only at first position . and then the first swap is just like swap(2,2)....which can be avoided with giving condition like if(i!=PIndex) swap(A[i],a[PIndex]);
What if we take pivot as (start + end)/2?
How he written the equation in 18:22
Thanks. k will be n-1 not n at 14:30
please upload a video on heap sort using c++
Really helpful, thank you.
What's wrong in my code
int arr[]={4, 5, 6, 2, 1, 7, 10, 3, 8, 9};
int size=sizeof(arr)/sizeof(arr[0]);
quickSort(arr, 0, size-1);
void quickSort(int arr[], int low, int high)
{
if(low>=high) return;
int partionIndex=randmized_partition(arr, low, high);
quickSort(arr, low, partionIndex-1);
quickSort(arr, partionIndex+1, high);
}
int partition_arr(int arr[], int low, int high)
{
int pivot=arr[high];
int partionIndex=low;
for(int i=low;i
please post a video on heap sort
wow explanation. Thank you
please,upload heap sort.
plz make a video on heap sort also
the narrator is alife , his friend who is dead .
Expressing T(n) in terms of T(1) , in that case n/2^k = 1. Can you please explain this?
At each step n is being divided by 2 to get n/2, then n/4, then n/8 and so on. In general it is T(n/2^k) with k being the number of times we've done that division. (Try this out for different values of k if you find it confusing) We want to take that expression to the base case of T(1) at which point n/2^k = 1.
Hope this helps.
t(n) = 2{2T(n/4) + c.n/2} + c.n
Why do you have the extra c.n?
Because of partition function
Can u plz upload the code implementation of "Merge Sort" also plz..........
Heap sort and radix sort algorithms?
If we draw recursion tree that would be much easy to understand.
if n-k=1, then how is n=k? it should be k=n-1. at time 14.33
yes, it should be n-k=0, hence k=n
Please do SHELL SORT and HEAP SORT
🤓🤓
where is the math of calculating the average case complexity i was not able to find it
well done !!
why space complexity is o(logn) for quick sort
chandrahas kondle its memory taken for recursion.
very nice video