CS50 2020 - Lecture 3 - Algorithms

TABLE OF CONTENTS

00:00:00 - Introduction
00:00:49 - ddb
00:02:53 - Arrays
00:05:08 - Searching
00:06:40 - Running Times
00:13:02 - Linear Search
00:22:57 - Binary Search
00:31:44 - numbers
00:37:58 - names
00:41:00 - strcmp
00:51:21 - structs
00:55:35 - phonebook
01:14:41 - Selection Sort
01:36:22 - Bubble Sort
01:54:32 - Recursion
02:04:22 - Merge Sort
02:23:00 - Visualizations

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David J. Malan

[unqueue]

For those of you who are wondering if CS50 is worth it.
1 year ago today, I was left without a job, I was working in hospitality and when the pandemic hit, everything closed.
For as far as I can remember I was intrigued by programming and computers and decided to learn how to code.
After dabbling around for a bit, I found CS50 and let me tell you, this course literally changed my life.
It took me around 2 months to finish, I had moments when I felt like a genius and moments when I almost gave up ( TIDEMAN ) but I kept going and I got to the end.
After this I've done the CS50 web programming and finished that aswell.
These two courses were a PERFECT combination to lay the foundations. Because I understood the basics, it was "easy" to keep on learning.
Now here I am, 1 year later, working in a web development company, and I sometimes find myself explaining basic concepts to mid-senior engineers.
THANK YOU David, Brian, Doug for this amazing resource of knowledge.

[munnycodes]

Even when Caleb asked that question that forced an error for the lecturer. He humbly took apart his code and explained why the result is wrong and how bugs are still common even if you've got a tonne of experience. This lecture is just incredible!

[kosan]

He's so enthusiastic in his teaching, he literally has sweat on his forehead. Mad respect.

[sejinmajnaric]

I'm grateful that this is accessible to all. Thank you, CS50 team!

[giovannitertulli]

The way they explain the efficiency of algorithms, both visually and in words, is just outstanding. This lecture was incredible. The fact that it is available to anybody for free and so easy to follow, even to a total starter like me, provokes some tears of joy.

[LavenderSpringfell]

It's wonderful how the professor approached the bug situation in a pedagogical way, it helped me understand the topic so much better.

[destinydecember]

linear search: upper bound- O(n), lower bound O(1)
binary search: upper bound - O(logn), lower bound O(1)
selection sort: upper bound - O(n^2), lower bound O(n^2)
bubble sort: upper bound - O(n^2), lower bound- O(n)
merge sort: upper bound- O(N log N), lower bound - O(n logn)
recursion

[Peredjes]

Vanna White: I was the most iconic hostess in television history
Brian Yu: Hold my integer

[MrBrancomusic]

Amazing! I much prefer this new version to the old one, it goes more into detail and is easier for me to understand how things work.
Thank you!

[Junior-nmmf]

46:02 Every programmer’s face when they are dumbfounded, even if only for a second.

[liss]

Professor David you're the best teacher I have seen online. With your knowledge, mastery of the content, the way you deliver it, your energy and enthusiasm is unmatched. With that kind of characteristics as yours I am sure you have drawn almost everyone across the globe to come and join CS50. You make the biggest population of students for this course. If everyone discovers you teaching online I can see a lot of potentials that would be developed within every students of yours and you would have. They will be encouraged to learn CS50, master it, enjoy it, share that energy and the great thing about CS50 to their friends, to the world, and better yet produce a wonderful output that can change their community for good and make a big change on their lives. We would be going back to say an endless thanks and appreciation to such wonderful professor that we all love and admire. Stay fit and healthy @David J. Malan

[deadnight]

❤️ This was by far the best explanation I've seen on this topic on computation. David Sir you are the best!! God bless CS50 Team behind running the show.

[uzorani]

CS50 is a goldmine! A real bonanza!
My LOVE to anyone teaching it, whether you did so on camera or worked behind the scenes. :-D

[pbr]

I studied computer science 15 years ago, but in my professional life I almost never had to program anything. To refresh my knowledge I am taking this course and for the first time I really enjoy listening to a programming course. This course is impressively well done. It's fun to hear and to go along with the examples. The usual problem of frustration never arises. Many thanks to the staff and to David Malan. Really very well done.

[greylarkan]

Revisited after 3 years out of school. Still learned alot. I also have 3 years professional exp. David is the man

[starfart]

the mistake made around 41:30 helped a lot more than I expected. I learned the reason why it's okay to just call the expression if the function return is boolean among others

[ussuraj]

That orchestra piece in the end though!! Goosebumps!! Amazing work you all!

[demolazer]

After struggling with the concept of algorithmic complexity for a while, the part transitioning from selection to bubble sort lit a lightbulb in my head. A phenomenal lecture.

[watashibr]

There are 3 things that keeps me focused on the CS50. The opening and ending theme, the Professor David passion for teach and now my best friend CS50 IDE Rubber Duck Debugging, quack! Keep it focused, where I live, is almost a "Mission Impossible"... Thank you, quack, quack!

[saadshah]

Harvard got its high repute name because of talented and enthusiastic teachers like these 🏆🏆🌟