Data Structures: Crash Course Computer Science #14
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- čas přidán 30. 05. 2017
- Today we’re going to talk about on how we organize the data we use on our devices. You might remember last episode we walked through some sorting algorithms, but skipped over how the information actually got there in the first place! And it is this ability to store and access information in a structured and meaningful way that is crucial to programming. From strings, pointers, and nodes, to heaps, trees, and stacks get ready for an ARRAY of new terminology and concepts.
Ps. Have you had the chance to play the Grace Hopper game we made in episode 12. Check it out here! thoughtcafe.ca/hopper/
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I told my friends that I now know how to access a 5 dimension matrix. They are no longer my friends.
Just remember, if you are new, that this 10m video is a 1 semester or a few books study compressed, so take it lightly.
They've explained it better here than at my college... I should be laughing, but it hurts.
lol my school started this like over a month ago and still hasn't finished XD. But its pretty simple tbh
Proof that one on one IS more efficient than telling a group of people to memorize datum.
Am I doing it wrong? I've binge watched up until now, and I plan on continuing until the end. FORTY SEMESTERS WORTH OF COMP SCI IN TWO DAYS!!!
@@aboxinspace Ditto. I am revisiting it 2 years later and I am just amazed how well it explained the concepts in just ten minutes. It helps though having studied it before in my opinion though.
the videos always seem like a compressed version of my first two years of studying computer science. though not as thorough as the lectures back then, these videos really hold up and explain everything extremely well. great job!
Crash course is a great way to refresh your knowledge about almost anything.
Data structures was my favorite subject in my CS courses in college! It all just makes so much sense, and thinking about how each piece of data relates to all the others is like a fun puzzle.
0:59
"Almost all programming languages start at index zero"
Me: *slowly turns and glares at Matlab*
MaTLaB Is NoT a ReAl ProGrAmMiNg LanGuAge
Pascal does this as well
*shouts at LUA*
@Thomas Samoht you are right, my bad.
LUA starts at 1 for some reason
I'm trying to get my teacher friends to show this series to their students. I love this. All students should see this in class.
For anyone who may just be starting to learn low level languages, be careful when using "NUL" vs "NULL" because they can mean two different things. "NUL" refers to the NUL character or ASCII zero. "NULL" refers to a null pointer - a reference to a non-existent location in memory.
"Null" is its name and NULL was its original abbreviation. So not as wrong as all that. en.wikipedia.org/wiki/ASCII
NULL could also be nullptr. NUL can also be '\0' (char type).
thanks much sir
Thank you
this is an awesome series. i was honestly expecting it to just barely skim the surface of this topic, but it's actually going in to a fair amount of detail. i love it.
Always great folks but that was pretty much an entire term's class-worth of data structures in 10 mins. It'd be fascinating to know how many people who encountered this for the first time kept up!
As a side-note it's really good how you refer everything back to memory locations. So often these days people are taught to use data structures as basic language building blocks with no idea what's going on "under the hood".
So, object orientation next week? :-)
Yep, nice but very, very concentrated. As I was listening I too thought that it might be hard to follow or even a bit misleading for a person new to the material. Universal referents and particular implementations got a bit tangled up. Still, an impressive effort given the time constraint.
Interesting. As a C# programmer did you find the discussion of stings at all confusing?
In my college is the opposite, and we had to build a Java class implementing the basic of each and one of the structures that the video showns. For example in an exam I had we needed to implement a funcion in a binary tree in wich we pass an array of numbers in any order and then the numbers got stored in the tree in order.
+Pepys
Thanks, maybe my criticism was misplaced. I suspected that people would watch that and think "oh, that's what a sting ~is~" rather than "that's one good way to implement a string." Your mention of C# jumped out at me since it is an example of a language that does strings differently than presented.
Sorry that I misinterpreted your programming experience.
Many CrashCourse episodes are like crammed with a little too much info to get in one pass. Sociology for example.
I tended to work with languages that were weak in data structures so I had to create my own with strings. Slow, but a great way to learn about data structures. (Hint: the secret is to have a delimiter character for each dimension that is never included in the data content.)
Dear Carrie Anne and crashcourse, I hope you're seeing this.
You are all amazing. Thanks so much for making these very good quality videos and keeping them for free.
I'm considering supporting you after I'm done with binge watching the entire series. I'll definitely recommend this series to others.
I'm impressed. You're amazing.
"It'd be weird if roots connected to leaves that connected to roots." *Looks nervously at Bryophyllum daigremontianum* >_>
Found the botanist! Seriously though, that's a dope plant.
I am happy you are here :)
I think most people would be freaked out a lil by how peanuts grow.
I'm learning to Program now, and surprisingly understood everything. Had to stop and scroll back a few times, but that was a beautifully clear explanation of each concept!
right now I just hope this will be a never-ending course
I am LOVING THIS SERIES! LOVE YOU CARRIE ANNE AND CRASH COURSE!
This series is why I'm getting into arduino programming, and this video just helped me get past a hurdle I encountered on my project. Thanks! =D
I love these videos and feel that I am actually finally understanding computers! thank you
dont mean to be rude or discouraging, but this is basically nothing ;(
this series is like my hit of crack every week that keeps me going
I'm a computer engineer and I'm doing some Java stuff for like 5 years, and this video gave me the envy to go back doing some C again, like I did back at school.
And I like that.
i am so in love with the narrator.She is so adorable !
You didn't play the "A new level of abstraction!" jingle! How could you?!
It's the same abstraction.
I feel cheated. I demand a reupload with proper jingle.
It has been abstracted so it's no longer shown.
I love the jingle and spontaneously combust whenever it comes on.
Anthony Z Soo you catch on fire?!?
Note that in some languages, strings are not null-terminated, but rather they start with how many characters the string contains. There's pros and cons to each approach.
(Also, the C++ standard library is called the Standard Library. The standard template library used to be a non-standard library that has since been added to the standard.)
As someone studying computer science, this is a fantastic refresher of all the basic concepts. So clearly explained!
You basically covered last semester programing course in a 10 min video, I am impressed. But it might be too much information for people who are seeing the topic for the first time.
Wow. This was super fast! If I didn't already know this stuff, I could easily get lost in all the information!
Spent the whole semester for this. Thank you!
You guys are amazing! I have my interviews in the next two weeks and this really helps me speed up
What a great Video!! such clever use of graphics and sounds in education....I enjoyed it wholeheartedly
im currently doing a course on data structures and we've only just reached pointer variables so this video is linking everything tgr before I've even learned it. cheers
You said in the beginning you weren't gonna go into programming yet I feel like I've learned a ton about the fundamentals of code languages and where programming happens. You tricked me into learning way too much!
Thank you! Now I understand why I always got errors when Iworked with Arrays. They don't want to grow dynamicly^^
God I love crash course :) I only wish you made actual courses on this subject. I am a currently earning my BS in CS and I absolutely love to talk about data structures. Programming is my blood. However, there are so many techniques and different ways to structure your data that I want to know everything I can.
i just love this woman, thank you so much
one thing left out in this otherwise really good overview is the main disadvantage of linked lists: random access (that is, getting the value at a certain index into the list) becomes much more difficult, and is much less efficient than in simple arrays. each data structure has its tradeoffs and use cases
This series is so clearly and helpful.
Good job giving us an easy to understand taste of different data structures
This is the fastest coverage of basic data structures I have ever seen
So good! Thank you for the excellent summary
Wonderful episode and series!! Thank you guys! I wish you showed a more in depth example of the push/pop with link nodes graphically to help. Matrix too lol great job, I'd love 15-30 mins eps just you know you :p
... Always end up watching them 3 times anyway lol
Addendum: Null character terminated strings are the most common way of doing it, but it's also possible to just store the length of the string as a number as the first field, then the string. Then, we know where to stop because we see the length before reading the string.
I love how the oscilloscope is different each time
Thanks a lot. I enjoyed the crash course. I now know what data structures are. planning to delve deeper
Wow..........this was best for my quick revision of DS. Thanks @CrashCourse!!
Great video good for those who have studied already these concepts in detail
A lot of programming languages are very particular about the type of data you give to a function, whereas more flexible ones can accept multiple types. The trade off is inflexibility against precision.
Sam Whelan some programming languages don't let you play with pointers.
A$= "at"+10+"shun"
The main drawback is that miss-typing isn't caught until the system tries to do an operation expecting one type and you give it another.
Static typing generally catches this before any of your code gets run.
Even worse is when the system preforms a different operation because it's a different type. The first time I used python, 10 < 5.
Here in México in my college they teach you about all of this plus the paradigm of object-oriented programming in two courses, called "Object-oriented algorithms and linear storage patterns" and "Object-oriented algorithms and non-linear storage patterns", We just call them by the initials, wich in spanish are APALOO and APANLOO, respectively.
0:44 list != array
An list uses pointers to get to the next index. An array uses ons block of memory. Meaning that a list is faster if you are iterating over the shops structure, but An array is better of you need to het a specific indexeert element.
would love to see a video on heap and hash in this format!
Yes! Another episode! I've beeeen waiting! 😃
Create complex data structure just really similar as you create a pile of structured files and folders in windowsOS, the pointer similar as shortcut that point to a folder or file in windows, so you can create linked data.
Another fantastic video. Should help me with my Algorithms exam tomorrow 😊.
I'm surprised you did touch on classes and its differences from structures. Good show!
Hello, Carrie Anne:
Your explanations and videos are great!!! Thank you so much for helping me understand computing better.
Small petition (although given my ignorance it may be huge X-D):
Could you please say or list the levels of abstraction required to display, for example, a "C" on a computer screen? 20+?
Thanks again for being awesome :-)
Miguel
Cool video, very well explained!
I think these videos are sooo interesting. wish their were more
hopefully you will talk about data hashing, this is crucially important in the modern world of programming.
I can't feel time by hearing your voice
It's just awsome
Really nice lesson, keep it up! 😁
A string doesn't necessarily terminate in a null. Although this is typical in C-like languages, many other languages store strings with the length of the string, eliminating the need for null terminating. (and allowing the null character to be included in a string)
Thanks a lot!😃
Excellently Explained...
Great video, easily digestible content
Excellent summary!
Crash Course Computer Science! Amazing.
She is so much more preferable to my monotone prof! I'm learning heaps - THX
What was that bit, just after the opening, and continuing to the end?
thanks for mentioning string cat. Super useful
Very basic but still awesome! Thanks
Is that an Arduino in the background using a sound sensor to light an LED?
Awesome videos...Thank you!!
"Standard Template Library" is the old name. It's the C++ Standard Library now. Glad C++ got a shout-out anyway.
Hell yeah someone else likes c++
wow an actual video where I knew about evrrything and wasn’t confused at any time during it??
Very good summary!
Excellent brief info!
How could you use a command like print to print past the end of a string into another memory location? I remember doing some type of code injection on a form to retrieve values in memory from a webpage that doesn't sanitize input back in college. That was awhile ago, I should search that up again. Btw this was in a lab class, I wasn't doing this maliciously.
Graphs are usually stored as list of nodes and tuples of edges.
This course is so good. They weren't mentioned but K-D trees frustrate me a lot
Told my friends I know how to access a 5 dimensionnal matrix. They were impressed!
If string concatenation = a strcat
Then does a string array = stingray?
stringray
strcat = string catenation
catenation and concatenation are synonyms but strcat has more obvious meaning than strcon, so that's why it was chosen for a name of the method (I presume).
Stringray, strray, and strarr are three likely candidates.
strarray, but I can see the intention of the joke.
String Array = Fruit of the Loom
Strings don't always end with a NULL. Sometimes they have a byte or word at the beginning that declares the length, though that's fairly uncommon.
Not all strings need to end in NULL. Seeing as strings are just arrays, and some languages store the length of an array, a string's length would just use the same value.
True, and both ways have their advantages and disadvantages. Let's say you have a really long string, like loading an entire file (not generally a good idea to load it into a string, use buffers or something instead, but this is an example), then null-terminated strings are smaller, as you'd need more than the size of a character to represent the length of the string if the string stored its length up-front, while the null-terminated string would only add the size of an additional character. Now this isn't a large amount of space, but because scenarios like this exist, the string data type in many languages use large numbers like ints or longs, even if the string is only very short, meaning if you're using hundreds or thousands of strings in a program (for example think about localization files for programs or games) then you're using up a lot more memory this way.
On the other extreme though, there are many calculations where you want to know the size of the array, but don't wish to modify or read the array, just know its size, in a null-terminated string the entire array must be iterated down until the null is found to calculate the size (it can possibly be stored afterwards so you only iterate once, but anyways) while storing the size up-front allows you to simply read this value, making these types of operations faster.
So both have some advantages and disadvantages and if you're lucky enough to be using a language where you can choose to use either or then choose based on the task, and otherwise other languages that don't have them sometimes have ways for you to implement them yourself if need be.
There is one more disadvantage of null-terminated strings: you cannot store nulls inside the string, as they are interpreted as termination signs.
If you store your strings as immutable structures in memory, the size issues kind of vanish, depending on whether or not length references number of bytes, or number of UTF-8 glyph encodings(Which can be different). Moreover, you can have multiple variants of "String" all implementing the same interface, and encoding length as different width values in the structure. Though, as soon as you get past the length being one byte, it's pretty valid to stop caring about what data type you're encoding length as(Max for a 1 byte value is 1:256).
Now, if they ARE mutable, things get fun, and you get into heuristically predicting the possible max size of your string, and giving it a data type wide enough for... however long your string gets. Granted, if your string gets beyond about 9 QUINTILLION characters(on a 64-bit processor, which is the modern standard) you have a very different problem.
All told, storing the length of strings has a great many advantages over not doing so, and most modern languages DO do so, because most concerns of space sort of evaporate in the face of modern hardware, and the vast amounts of memory available(Not to mention the fact that 8 bytes to store the lengths of the longest things humans have ever written PALES in comparison to what 8 bytes of length can store)
The main problem with null terminated strings is that you have to be careful of the target size of the character array, this is why you should use strncat rather than strcat. Also it is easier to resize a target string because you can easily determine the size of the strings without traversing the source arrays then allocate the desired memory and do the copy. In fact overall null terminated strings are considered unsafe programming because there is the risk of someone using a buffer overflow to hack you if you don't carefully determine the lengths.
+Piotr Zaborski you typically wouldn't want to stored null characters in a string, it's a special character
love the geeky GoT examples!
Theres no elevator scene after the new level of abstraction!!!! Argh i watch this every week for that!!!!
You haven't talked about the more complicated data structures like Segment trees, Fenwick trees, Red black trees, Trie, Suffix tree, Suffix array , Wavelet trees which can do quite a lot!!
I like this series!😀😊👍
Was that a bong on the table on the picture of the dorm room next to the Xbox controller?
Is this up for malloc/memory allocation next?
hey! you didn't play the new level of abstraction clip!
Is that so bad? It's like 5 seconds long and I kinda just sit there like "yeah, I get it hahahaaa"
Mongols are the exception to being the next level of abstraction.
That's device dependent.
Carrie Anne
Gah! Holding out on me with the "next level of abstraction" graphic.
This should have been in the Sylladex training course.
That algorithm that allows this video to be played at half speed....that's a favorite of mine
This is why we always say zeroth instead of first.
it is easy to understand thankyou
Error after 7.30 - Doubly linked list is explained as Tree.
What are the uses of linked lists?Can anyone explain(briefly) with an example?
I'm glad l managed to pop my cellphone out of my sylladex so l could watch this video.
Boi I sure hope this all makes sense in 3 years when I have to learned this
What is a struct?? I'm not getting things clearly after 4:05
How long are the pointer values in terms of bytes?
Bruh I studied this for an entire semester and all I got out of it that she didn't cover was pqueues, skiplists, red-black, AVL trees, hashtables, sparse matrices and heaps. Heaps and hashmaps definitely would have been a good to cover here those are super useful and not just minor variations on a general theme.