Hope you all enjoyed the latest addition to the C++ series! Let me know if you have any questions about maps below 👇 Also definitely check out Hostinger for all your web hosting needs, and use coupon code CHERNO for a discount: hostinger.com/cherno

21:01 - When using find(), you can avoid the second lookup required by at() by saving the iterator returned by find(). For example: if (const auto it = cities.find("Berlin"); it != cities.end()) { const CityRecord& berlinData = it->second; // ... } I recommend always doing this whenever you use find() to do a lookup. If you only need to know whether the element exists or not, you can use ".count(key) != 0" (or ".contains(key)" in C++20) instead.

Hey Cherno, would love a “productivity in c++” kind of video maybe going over keyboard shortcuts or ways to code more efficiently in visual studio or just in general

since when Mr. Beast is teaching programming???

The find + at pattern at 20:50 does twice the amount of necessary work, because find already returns a pointer to the data.

15:20 A hash function is not required to return a unique hash. Two things with the same hash will be stored in the same bucket, which is inefficient for lookups, but it will function fine. The hash provides fast access to the appropriate bucket. The equality operator is what determines if a key actually matches. You should strive to make unique hashes for performance reasons, but hash collisions will not compromise the map. 26:50 -If two cities have the same population and that is all you are using for comparison, then they will appear in an arbitrary order but still appear next to each other in the map. Nothing is broken in this case. You just will not be able to rely on their order remaining consistent as the map changes.- This is incorrect. Not sure what I was thinking when I wrote it.

Thanks for your videos Cherno. I only just stumbled across your channel and your videos have been a really useful recap for my rusty C++ skills from over a decade ago!

Yes! This C++ series is truly a gold mine :D

Oh nice. Finally a video for the C++ series. I got so excited when I saw the notification.

100/100 c++ videos from this playlist watched! Been very informative so thanks for this series!

Thank you so much to put more content in this series. Waiting for more videos on data structures

I love this little focus videos man. Keep it up!

Yes!! Continue this series I love it!!!

Appreciate this series so much!

I was almost two weeks behind on my assigment. this helped me to finally get the courage and finish it. thanks!

15:51 What you're trying to do is called aggregate initialization. It requires you to also use curly brackets. Unfortunately you'll need to use push_back instead of emplace_back because the parameters aren't passed through, but the object is first created and then passed through. Thanks for the great content. Keep them coming!!

Great video! A follow up video about std::set in which you compare the different sets to the different maps would be awesome! Keep it up!

Yes !!!, Thanks so much for these. Please more on c++ data structures

Hey Cherno, I started watching you 5 years ago, while I was in my first year of college. I saw every video you made. I patiently rewrote line by line your sparky engine, but then I had so many school duties and I had to start working to pay for the college, so that I had to stop following you. Now 5 years later I'm back and ready to continue. I don't know what is so magical about working with OpenGL and graphics, but it's still my dream job to work with OpenGL. I tried many specialization like neural nets, hardware design in VHDL, motor control, image processing but nothing got me interested as OpenGL. Best part of college was C++ course, where I applied everything you taught me. Thank you so much for your content and god bless your family.

100th video of the c++ series. Well done Yan!!

Thanks for c++ tutorial/series. You're amazing keep on

Very well explained , appreciate for your hard work and honest effort !!

Thank you very much for all the explanations and examples, Cherno! Would definitely love to see a benchmark comparison for various kinds of maps! On a separate note, you once mentioned thinking about a video on variadic templates - would be excited to see that one too!

Gold, I'd expect nothing less. Thanks Cherno

This is so cool! I was just doing a Clash of Code on CodingGame yesterday and asking a guy about these! Now, you're posting a video on them: A nice coincidence!

One important thing to mention is that the std:: (unordered-)map/set containers are very slow, because they need to guarantee pointer stability and abi breaks hinder compiler vendors from improving them. You can get speedups of sometimes up to 5x by just using a different hash map, e.g. absl::flat_hash_map or tsl::robin_map.

Fantastic channel! really nice to have as support when I'm studying. I think a video about concepts and constraints in C++20 would be interesting

Expecting more content in this C++ series. This series is a gem. 🔥

wow, i learned about at() throwing in the morning getting to work, and the same day I actually used this knowledge in my work process! so cool, never payed attention to that before

This video helped a ton. Thanks as always.

💯 completed. Thank You. Its a historic moment.

Waiting for this.... Thanks Man

Never would've thought I'd learn basic c++ in two weeks knowing just js but here we are. This series is wild.

Looking forward to the video of the performance between these maps!!!🤩

Keep streaming Yan, it makes my day.

Fantastic video for C++ learner！

I was already familiar with std::map, but i was not aware of the constness of the operator[] and how it always insert an element regardless, good stuff, keep it up ! Definitly interested to see a benchmark video !

Thank you, for saving my course project.

Finally a C++ series tutorial with an old style thumbnail!

Your videos are so funny and teach me a lots

Bro, perfect timing.

Thanks for reminding me of binary search. Haven't used that algo in years, mainly because the containers I work with tend to be unordered. But good to know, that you *could* use it.

your video is amazing

Awesome!

Finally! A new video!!!!!!!

!the best c++ channel

I missed this series so much buddy =]

Like your videos a lot, hope to see more of these! I will be nice if you could have videos about C++20 features. P.S You could have mention that c++20 has contains() for maps.

damn, in 10 seconds you've solved my c++20 problem. twas a hardly laugh to see that i've been rockin' C++14 the whole time

STL error/warning messages are so much fun to try and comprehend. At least C# custom hashing is wickedly easy to implement, albeit a bit challenging to implement "correctly" (with uniformly-distributed hash codes). All of this discussion about std::map, and you just lit the light bulb for a problem that I was dealing with. Thanks Cherno!

Great, thank you!

Great video as always. I'd be keen to see the performance benchmarking of standard and unordered maps. I've heard that there's a couple of dimensions to the problem, in particular if the keys, (when strings) often start with identical substrings (common issue naming keys, eg 'address_line_1', 'address_line_2' etc) as this affects how long the string comparisons take to find the location in the tree. So apparently ordered maps can be faster for small collections, where a very small tree search can outstip the hash function, and the transition point depends on how distinct (or overlapping) the start of the strings in the keys are on average. I haven't done any benchmarking myself, but would be great to see.

Sure, performance video about maps would be awesome!

Please continue this series

Thanks for the great videos. Yes, a video map benchmark please :)

Wow bro… you gat me dripping … I was just thinking of it about an hour ago…

When using string as a key for map it’s generally good to pass a string comparator func as well

I'm glad you're still doing these!! These video's help a lot. I''m not doing maps yet but I know I'll be back here in no time. I can't wait until I know enough to follow your code review videos!

Of course we want performance comparisons and/or performance measuring tips in general. :)

It has been a year, and i still want to see the performance comparison and more c++ series!!!

great video as always, you should give a talk at cppcon about teaching cpp next year

I love the honesty of how you handled the odditites in the industry, I love that you explain multiple ways of doing something even if there is a less conventional way as a just in case, I love that you actually explain how to read the error messages and output errors and most of all I love your accent. Thank you so much for being clear and connecting dots.

That is so fudging cool

I actually learned this today, would have liked to have this video a couple hours ago hahaha

You can have best of both worlds with an index map; store values in a Vec and a map of hashes to indexes. Although the tradeoff is that more memory is used.

Still going strong ? Happy to see you back :)

Glad this series is back!! It helped me a ton when learning c++

Another great video! I'd love to see a video where you write your own memory allocator, maybe talking about different ways to implement them, and what scenarios each way might provide a boost in performance for. I've been working on my own physics engine and took a lot of inspiration from Box2D which uses a couple of different custom allocators for different situations, and I'd love to learn more.

"Why are there two different types of maps? Because there are different types of maps." - Cherno 2022

Once again you summarize a key data structure better than my college professor.

you are basically screwed. absolutely loved that word "screwed".🤣🤣

Hey would love to see the performance benchmarks you mentioned towards the end of the video. Thanks for the brilliant content

15:48 Hey TheCherno, it can be solved by passing the arguments as "initializer list-looking" syntax, as emplace_back is requiring a single Object. So, the arguments have to be a single object. They can be: .emplace_back(CityRecord{ "CityName", 50000, 70, 70}); Or just, .emplace_back({ "CityName", 50000, 70, 70}); By the way, I'm a long-term TheCherno follower, and it's the first time I suggested something to my mentor :)

the equals sign is because of microsoft's new font having ligatures, you can disable it

also a video on how to implement a map in the stl way would be awesome, just like the vector and iterators videos you did :)

Thanks

Guy, i'm from Brazil, english not is my native language, but i need to say that this channel is my favorite font to learn and apply your content; Thank you for this video, i very like to be here. 🎯🚀

i would love a video going over a bunch of beginner, intermediate, advanced projects in c++ since yk the best way to learn to code is to...actually code lol

Nice

You are to C++ as Shakespeare is to the rhyming couplet - that was just great stuff....

This video reminded me of why I put off learning C++ for so long! I've been using C# for years and even learned C last year, but C++ still scared me lol. I was going through your playlist and following along pretty well and then I started skipping around... and well... That hash setup is gross XD. I'll stick with it tho!

A proper rigorous benchmark comparing map, unordered_map, and vector would be great. I constantly read benchmarks are meaningless because they weren't implemented correctly. It would be nice to see an example of that. It would also be nice to see a more sophisticated process than simply printing times from a timer. Perhaps memory usage and the underlying data structures that give rise to whether a map is ordered or not. Hell, cache friendliness of the three methods would be cool to see as well.

In C++20 you could do map.contains() to check if an element exists.

19:46 that`s why i love c++, sometimes it`s so tricky and unpredictible

so much. Can’t wait to start making soft.

Note that using std::pmr memory resources can significantly improve your containers performance, provided you set your memory resource objects appropriately.

Would love a video on performance benchmarks for maps and unordered maps

Thank you so much for your content. Can you make a video about unit testing in C++?

Спасибо! Заждался новых выпусков)

You provide very helpful information! Could you make a video on Variadics and List Initializer templates?

Python developers when Cherno says "Expensive" *cricket noises*

Perhaps this will dovetail nicely into a follow-up video on performance, but what do you think of the Slot Map data structure?

20:50 now you can use std::unordered_map::contains in c++20 instead of checking if find() equals the past-the-end

Nice video, however, at 15:31, when 2 keys give the same hash they don't necessarily map to the same element, they only do it when they compare equal, so, just returning 0 in the hash function will not break the unordered_map, it will only make it really slow. Also, your setup seems to implicityly define some constructors and operators as, with `g++ -std=c++17`, in the std::vector example you needed to define the constructor and for using a custom type for the key in a std::unordered_map it also needed defining operator==. I think you should mention that you also need to define something that would tell if 2 keys are equal

Holy shit at 25 minutes I was literally putting my plate down to ask you to cover the case that you literally IMMEDIATELY introduced as I touched my keyboard near the end of the video. Incredible, best CPP channel on the platform. Casual pace but advanced topics ♥️

at 21:18 you're searching for element twice, at "find" call and at "at" call The better way would be to get an iterator of "find" and then use iterator instead of "at" call For unordered_map it might be not that important but it is for a map

Creo que dentro de estos 100 vídeos que he visto, he visto su pelo crecer, cortarse, volver a crecer y cortarse, y así, siento que hasta seguí una especie de historia en libros junto a él y su cabello xD

Thank you, as always, I learn more from you than I would have ever even thought to ask. If you're looking for request though, I'd like to understand the hashing process. What is it doing with that string that somehow magically makes everything faster? Is the string converted to an int and then the int used as an index? How is that faster? I'm sure I'm not even asking the right question but I bet you could provide the right answer anyway because you have a deep understanding that I hope to get to at some point.

Thank you for another great video. I heard you say once that you're not a fan of exceptions. Do you still maintain that stance and did you ever do a video to explain what you meant by that?

Would love to see some Cmake stuff, I find I am able to get up and running with python, importing package and sharing code quickly, would be nice to see your approach with Cmake