title
CS50 2021 in HDR - Lecture 5 - Data Structures

description
This is CS50, Harvard University's Introduction to the intellectual enterprises of computer science and the art of programming. Enroll for free at https://cs50.edx.org/. Slides, source code, and more at https://cs50.harvard.edu/x. Playlist at https://www.youtube.com/playlist?list=PLhQjrBD2T383f9scHRNYJkior2VvYjpSL. TABLE OF CONTENTS 00:00:00 - Introduction 00:01:17 - Data Structures 00:02:25 - Arrays 00:09:41 - Arrays in C 00:23:50 - Realloc 00:26:34 - Arrow Notation 00:28:58 - Linked Lists 00:43:19 - Building a Linked List 00:51:29 - Linked Lists in C 01:10:09 - Linked List Demonstration 01:17:45 - Linked List Time Complexities 01:23:20 - Binary Search Trees 01:30:52 - tree.c 01:37:17 - Searching a Binary Search Tree 01:43:10 - Binary Search Tree Time Complexities 01:44:00 - Hash Tables 01:50:33 - Hash Functions 01:51:40 - Hashing Demonstration 01:53:25 - Buckets and Collisions 01:57:20 - Tries 02:04:04 - Stacks and Queues 02:08:23 - Jack Learns the Facts 02:12:14 - This was CS50 *** This is CS50, Harvard University's introduction to the intellectual enterprises of computer science and the art of programming. *** HOW TO SUBSCRIBE http://www.youtube.com/subscription_center?add_user=cs50tv HOW TO TAKE CS50 edX: https://cs50.edx.org/ Harvard Extension School: https://cs50.harvard.edu/extension Harvard Summer School: https://cs50.harvard.edu/summer OpenCourseWare: https://cs50.harvard.edu/x HOW TO JOIN CS50 COMMUNITIES Discord: https://discord.gg/cs50 Ed: https://cs50.harvard.edu/x/ed Facebook Group: https://www.facebook.com/groups/cs50/ Faceboook Page: https://www.facebook.com/cs50/ GitHub: https://github.com/cs50 Gitter: https://gitter.im/cs50/x Instagram: https://instagram.com/cs50 LinkedIn Group: https://www.linkedin.com/groups/7437240/ LinkedIn Page: https://www.linkedin.com/school/cs50/ Medium: https://cs50.medium.com/ Quora: https://www.quora.com/topic/CS50 Reddit: https://www.reddit.com/r/cs50/ Slack: https://cs50.edx.org/slack Snapchat: https://www.snapchat.com/add/cs50 SoundCloud: https://soundcloud.com/cs50 Stack Exchange: https://cs50.stackexchange.com/ TikTok: https://www.tiktok.com/@cs50 Twitter: https://twitter.com/cs50 YouTube: http://www.youtube.com/cs50 HOW TO FOLLOW DAVID J. MALAN Facebook: https://www.facebook.com/dmalan GitHub: https://github.com/dmalan Instagram: https://www.instagram.com/davidjmalan/ LinkedIn: https://www.linkedin.com/in/malan/ Quora: https://www.quora.com/profile/David-J-Malan TikTok: https://www.tiktok.com/@davidjmalan Twitter: https://twitter.com/davidjmalan *** CS50 SHOP https://cs50.harvardshop.com/ *** LICENSE CC BY-NC-SA 4.0 Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International Public License https://creativecommons.org/licenses/by-nc-sa/4.0/ David J. Malan https://cs.harvard.edu/malan malan@harvard.edu

detail
{'title': 'CS50 2021 in HDR - Lecture 5 - Data Structures', 'heatmap': [{'end': 1760.453, 'start': 1513.002, 'weight': 0.972}, {'end': 2313.929, 'start': 2233.57, 'weight': 0.803}, {'end': 2794.795, 'start': 2550.279, 'weight': 0.93}, {'end': 3355.944, 'start': 3187.37, 'weight': 0.918}, {'end': 3992.868, 'start': 3906.693, 'weight': 0.73}, {'end': 5587.026, 'start': 5498.47, 'weight': 0.821}, {'end': 6621.232, 'start': 6538.726, 'weight': 0.931}], 'summary': 'Covers transitioning to python, array manipulation in c, memory management, linked lists, memory allocation, programming challenges, binary search tree implementation, data structures and algorithms, trie data structures, and abstract data structures with a focus on simplification, increased functionality, big o notation, memory optimization, linked list manipulation, binary search tree creation, hash table applications, sorting algorithms, and practical use cases of abstract data structures in various scenarios.', 'chapters': [{'end': 546.254, 'segs': [{'end': 371.079, 'src': 'embed', 'start': 344.976, 'weight': 4, 'content': [{'end': 350.139, 'text': "And then ultimately, once I'm ready to fill the 4, I can throw away essentially the old array at this point,", 'start': 344.976, 'duration': 5.163}, {'end': 352.001, 'text': 'because I have it now entirely in duplicate.', 'start': 350.139, 'duration': 1.862}, {'end': 354.002, 'text': 'And I can populate it with the number 4.', 'start': 352.401, 'duration': 1.601}, {'end': 355.663, 'text': 'All right, so problem solved.', 'start': 354.002, 'duration': 1.661}, {'end': 358.405, 'text': 'That is a correct potential solution to this problem.', 'start': 355.683, 'duration': 2.722}, {'end': 361.927, 'text': "But what's the trade-off? And this is something we're going to start thinking about all the more.", 'start': 358.805, 'duration': 3.122}, {'end': 368.299, 'text': "What's the downside of having solved this problem in this way? Yeah? Yeah, I'm adding a lot of running time.", 'start': 362.368, 'duration': 5.931}, {'end': 371.079, 'text': 'It took me a lot of effort to copy those additional numbers.', 'start': 368.339, 'duration': 2.74}], 'summary': 'Filling array with 4 duplicates adds running time.', 'duration': 26.103, 'max_score': 344.976, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU344976.jpg'}, {'end': 410.677, 'src': 'embed', 'start': 375.141, 'weight': 0, 'content': [{'end': 382.403, 'text': 'But if we start talking about interesting data sets, sort of web application data sets, mobile app data sets, where you have not just a few,', 'start': 375.141, 'duration': 7.262}, {'end': 389.345, 'text': 'but maybe a few hundred, a few thousand, a few million pieces of data, this is probably kind of a suboptimal solution to just oh,', 'start': 382.403, 'duration': 6.942}, {'end': 391.226, 'text': 'move all your data from one place to another.', 'start': 389.345, 'duration': 1.881}, {'end': 394.547, 'text': "Because who's to say that we're not going to paint ourselves into a new corner?", 'start': 391.546, 'duration': 3.001}, {'end': 401.351, 'text': "It would feel like you're wasting all of this time moving stuff around and ultimately just costing yourself a huge amount of time.", 'start': 394.707, 'duration': 6.644}, {'end': 410.677, 'text': 'In fact, if we put this now into the context of our big O notation from a few weeks back, what might the running time now of search be for an array?', 'start': 401.631, 'duration': 9.046}], 'summary': 'Moving large data sets can lead to inefficiency and time wastage.', 'duration': 35.536, 'max_score': 375.141, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU375141.jpg'}, {'end': 464.182, 'src': 'embed', 'start': 439.361, 'weight': 3, 'content': [{'end': 445.826, 'text': 'OK, yeah, so if we go through each element, for instance from left to right, then search is going to take us big O running time.', 'start': 439.361, 'duration': 6.465}, {'end': 453.151, 'text': "If, though, we're talking about these numbers specifically and now I'll explicitly stipulate that, yeah, they're sorted does that buy us anything?", 'start': 446.246, 'duration': 6.905}, {'end': 459.455, 'text': 'What would the big O notation be for searching an array in this case, be it of size 3 or 4 or n?', 'start': 453.211, 'duration': 6.244}, {'end': 464.182, 'text': 'more generally? Big O of not n, but rather log n right?', 'start': 459.455, 'duration': 4.727}], 'summary': 'Searching a sorted array reduces big o from n to log n.', 'duration': 24.821, 'max_score': 439.361, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU439361.jpg'}], 'start': 79.329, 'title': 'Transitioning to python and data structures', 'summary': 'Discusses transitioning from c to python, emphasizing simplification, increased functionality, and utilizing pre-written frameworks. it also covers challenges with arrays, trade-offs of copying data, and implications for search and insertion operations in terms of big o notation.', 'chapters': [{'end': 134.017, 'start': 79.329, 'title': 'Transition to python', 'summary': 'Discusses the transition from c to python, highlighting the simplification and increased functionality, with the ability to accomplish more with fewer lines of code and utilize pre-written frameworks and libraries.', 'duration': 54.688, 'highlights': ['Python transition marks the end of C in CS50, offering simpler syntax and increased functionality with just single lines of code.', 'In Python, users will be able to leverage more code from other people through libraries and frameworks, allowing them to accomplish more with less effort.', 'Introduction of Python will reduce the low-level plumbing and frustration experienced with C, granting the ability to do more with single lines of code.']}, {'end': 546.254, 'start': 134.017, 'title': 'Understanding data structures and memory management', 'summary': 'Discusses the challenges with arrays, the trade-offs of copying data to solve problems, and the impact on running time, highlighting the suboptimal solutions and the implications for search and insertion operations in terms of big o notation.', 'duration': 412.237, 'highlights': ['The trade-off of copying data to solve problems Copying data to solve problems can lead to increased running time, especially with large data sets, impacting the efficiency of search and insertion operations.', 'The implications for search and insertion operations in terms of big O notation Search operations remain in big O of log n when using arrays, while insertion operations become big O of n due to the need to copy existing data, which can result in a cumulative impact on the efficiency of the program.', 'Challenges with arrays and the impact on running time The challenges with arrays, such as the need to copy data for insertion, can result in suboptimal solutions and increased running time, particularly with large data sets, affecting the performance of computer programs and applications.']}], 'duration': 466.925, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU79329.jpg', 'highlights': ['Python transition marks the end of C in CS50, offering simpler syntax and increased functionality with just single lines of code.', 'Introduction of Python will reduce the low-level plumbing and frustration experienced with C, granting the ability to do more with single lines of code.', 'In Python, users will be able to leverage more code from other people through libraries and frameworks, allowing them to accomplish more with less effort.', 'The trade-off of copying data to solve problems can lead to increased running time, especially with large data sets, impacting the efficiency of search and insertion operations.', 'The implications for search and insertion operations in terms of big O notation: Search operations remain in big O of log n when using arrays, while insertion operations become big O of n due to the need to copy existing data, which can result in a cumulative impact on the efficiency of the program.', 'Challenges with arrays, such as the need to copy data for insertion, can result in suboptimal solutions and increased running time, particularly with large data sets, affecting the performance of computer programs and applications.']}, {'end': 1593.677, 'segs': [{'end': 715.396, 'src': 'embed', 'start': 689.126, 'weight': 3, 'content': [{'end': 697.269, 'text': 'So what this is going to do for me is give me enough memory for that very first picture we drew on the board, which was the array containing 1,, 2,', 'start': 689.126, 'duration': 8.143}, {'end': 701.81, 'text': 'and 3, but laying the foundation to be able to resize it, which was ultimately the goal.', 'start': 697.269, 'duration': 4.541}, {'end': 703.771, 'text': 'So my syntax is a little different here.', 'start': 702.15, 'duration': 1.621}, {'end': 708.753, 'text': "I'm going to use malloc and get memory from the so-called heap, as we called it last week,", 'start': 704.271, 'duration': 4.482}, {'end': 715.396, 'text': 'instead of using the stack by just doing the previous version, where I said int list 3..', 'start': 708.753, 'duration': 6.643}], 'summary': 'Using malloc to get memory from heap for resizing array.', 'duration': 26.27, 'max_score': 689.126, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU689126.jpg'}, {'end': 800.736, 'src': 'embed', 'start': 768.609, 'weight': 1, 'content': [{'end': 770.551, 'text': 'And list bracket 2 will be 3.', 'start': 768.609, 'duration': 1.942}, {'end': 773.294, 'text': "So that's the same kind of syntax as before.", 'start': 770.551, 'duration': 2.743}, {'end': 775.736, 'text': 'And notice this equivalence.', 'start': 773.374, 'duration': 2.362}, {'end': 781.2, 'text': "Recall that there's this relationship between chunks of memory and arrays.", 'start': 776.636, 'duration': 4.564}, {'end': 785.484, 'text': 'And arrays are really just doing pointer arithmetic for you, where the square bracket notation is.', 'start': 781.3, 'duration': 4.184}, {'end': 790.768, 'text': "So if I've asked myself here in line 5 for enough memory for three integers,", 'start': 786.004, 'duration': 4.764}, {'end': 795.832, 'text': 'it is perfectly OK to treat it now like an array using square bracket notation,', 'start': 790.768, 'duration': 5.064}, {'end': 800.736, 'text': 'because the computer will do the arithmetic for me and find the first location, the second and the third.', 'start': 795.832, 'duration': 4.904}], 'summary': 'Memory chunks can be treated as arrays using square bracket notation, with 3 integers allocated.', 'duration': 32.127, 'max_score': 768.609, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU768609.jpg'}, {'end': 1261.434, 'src': 'embed', 'start': 1236.329, 'weight': 0, 'content': [{'end': 1243.931, 'text': 'then on this array-based approach, the first of which is statically allocating an array, so to speak, by just hard coding the number 3..', 'start': 1236.329, 'duration': 7.602}, {'end': 1249.673, 'text': 'The second version now is dynamically allocating the array using not the stack but the heap.', 'start': 1243.931, 'duration': 5.742}, {'end': 1255.595, 'text': 'But it, too, suffers from the slowness we described earlier of having to copy all those values from one to the other.', 'start': 1250.113, 'duration': 5.482}, {'end': 1257.015, 'text': 'OK, hand was over here.', 'start': 1255.895, 'duration': 1.12}, {'end': 1261.434, 'text': 'Good question.', 'start': 1260.973, 'duration': 0.461}], 'summary': 'Comparison of static and dynamic array allocation, both suffering from copying inefficiency.', 'duration': 25.105, 'max_score': 1236.329, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU1236329.jpg'}, {'end': 1420.381, 'src': 'embed', 'start': 1394.941, 'weight': 2, 'content': [{'end': 1399.945, 'text': 'So let me back up here and just now make one final edit.', 'start': 1394.941, 'duration': 5.004}, {'end': 1410.093, 'text': "So let's finish this with one final improvement here, because it turns out there's a somewhat better way to actually resize an array,", 'start': 1400.485, 'duration': 9.608}, {'end': 1411.133, 'text': "as we've been doing here.", 'start': 1410.093, 'duration': 1.04}, {'end': 1415.537, 'text': "And there's another function in standard lib that's called realloc for reallocate.", 'start': 1411.153, 'duration': 4.384}, {'end': 1420.381, 'text': "And I'm just going to go in and make a little bit of a change here so that I can do the following.", 'start': 1415.637, 'duration': 4.744}], 'summary': 'Discussing a final improvement to resize an array using realloc function.', 'duration': 25.44, 'max_score': 1394.941, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU1394941.jpg'}], 'start': 546.554, 'title': 'Array manipulation in c', 'summary': 'Covers omega notation in best-case search algorithms, array creation and printing in c, dynamic memory allocation for resizing arrays, and the introduction of the realloc function for streamlining the resizing process.', 'chapters': [{'end': 581.983, 'start': 546.554, 'title': 'Omega notation in best case', 'summary': 'Discusses the best case scenario for search algorithms, where the search could take one step in the most fortunate scenario, but might take n steps in the worst case, particularly in binary search or linear search, and also explores the possibility of inserting numbers with and without having to move existing elements.', 'duration': 35.429, 'highlights': ['The best case scenario for search algorithms may result in the search taking a single step, as the desired number could be found right in the middle, particularly in binary search or linear search.', "If there's enough room and no need to relocate existing numbers, inserting a new number may be achieved in one step, as suggested by putting the number 4 at the end.", 'In the worst case, the search algorithm might take n steps to find the desired number, as opposed to the fortunate scenario where it could take just one or a constant number of steps.']}, {'end': 834.599, 'start': 582.123, 'title': 'Creating and printing an array in c', 'summary': 'Demonstrates the process of creating and printing an array in c, initially in a static way and then dynamically, utilizing malloc to allocate memory and explaining the difference between stack and heap memory allocation.', 'duration': 252.476, 'highlights': ['The chapter demonstrates the process of creating and printing an array in C The chapter focuses on the step-by-step process of creating and printing an array in C, showcasing the transition from the old way of implementation to the dynamic allocation of memory.', 'Utilizing malloc to allocate memory The use of malloc to dynamically allocate memory for the array is highlighted, enabling the resizing of the array and providing a foundation for further memory manipulation.', 'Explaining the difference between stack and heap memory allocation The chapter explains the distinction between stack and heap memory allocation by comparing the traditional array creation method, which uses stack memory, with the dynamic allocation using malloc, which utilizes heap memory and allows for dynamic resizing.']}, {'end': 1058.568, 'start': 835.079, 'title': 'Dynamic memory allocation', 'summary': 'Discusses the problem of resizing an array dynamically, and presents a solution involving dynamic memory allocation, copying data, and updating the array.', 'duration': 223.489, 'highlights': ["The problem with the code is that it doesn't copy the original data when resizing the array, orphaning the original chunk of memory.", 'Using a temporary variable and dynamic memory allocation to copy the original data and add new elements resolves the issue.', 'The chapter emphasizes the importance of cleaning up memory using free after using malloc.', 'The process involves dynamically adding space to the array, copying the original data, and updating the array, ensuring successful resizing.']}, {'end': 1593.677, 'start': 1058.708, 'title': 'Dynamic memory allocation in c', 'summary': 'Explores the process of dynamically allocating and resizing an array in c, detailing the steps involved in allocating, copying, and freeing memory, as well as introducing the realloc function to streamline the resizing process.', 'duration': 534.969, 'highlights': ['The chapter discusses the process of dynamically allocating memory in C, including a safety check to ensure that memory is available before copying values and adding new elements to the array.', 'The process of freeing memory is crucial in dynamic memory allocation, as failing to do so can lead to memory leaks, as demonstrated by the use of Valgrind to identify memory issues.', 'The introduction of the realloc function is highlighted as a more efficient way to resize an array, as it can handle the process of moving the array to a new chunk of memory and freeing the old memory, streamlining the resizing process.']}], 'duration': 1047.123, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU546554.jpg', 'highlights': ['The introduction of the realloc function is highlighted as a more efficient way to resize an array, as it can handle the process of moving the array to a new chunk of memory and freeing the old memory, streamlining the resizing process.', 'The process of freeing memory is crucial in dynamic memory allocation, as failing to do so can lead to memory leaks, as demonstrated by the use of Valgrind to identify memory issues.', 'The process involves dynamically adding space to the array, copying the original data, and updating the array, ensuring successful resizing.', 'The chapter emphasizes the importance of cleaning up memory using free after using malloc.', 'Using a temporary variable and dynamic memory allocation to copy the original data and add new elements resolves the issue.']}, {'end': 2429.452, 'segs': [{'end': 1829.496, 'src': 'embed', 'start': 1800.939, 'weight': 6, 'content': [{'end': 1803.921, 'text': "It's not necessarily the case that it's literally back to back.", 'start': 1800.939, 'duration': 2.982}, {'end': 1810.663, 'text': 'That would have the downside, it would seem, of costing us a little bit of space, like a pointer which, recall, takes up some amount of space,', 'start': 1804.441, 'duration': 6.222}, {'end': 1812.664, 'text': 'typically 8 bytes or 64 bits.', 'start': 1810.663, 'duration': 2.001}, {'end': 1817.785, 'text': "But I don't have to copy, potentially, a huge amount of data just to add one more number.", 'start': 1813.124, 'duration': 4.661}, {'end': 1819.606, 'text': 'And so these things do have a name.', 'start': 1818.045, 'duration': 1.561}, {'end': 1822.207, 'text': 'And indeed, these things are what generally would be called a.', 'start': 1820.026, 'duration': 2.181}, {'end': 1825.094, 'text': 'Linked list.', 'start': 1824.173, 'duration': 0.921}, {'end': 1829.496, 'text': 'A linked list captures exactly that kind of intuition of linking together things in memory.', 'start': 1825.414, 'duration': 4.082}], 'summary': 'Using linked list can save space by not copying large amounts of data, typically 8 bytes or 64 bits.', 'duration': 28.557, 'max_score': 1800.939, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU1800939.jpg'}, {'end': 1884.998, 'src': 'embed', 'start': 1859.275, 'weight': 0, 'content': [{'end': 1863.8, 'text': 'And who knows? It ends up up there at location 0x123 for the sake of discussion.', 'start': 1859.275, 'duration': 4.525}, {'end': 1866.362, 'text': "All right, maybe there's something already here.", 'start': 1863.82, 'duration': 2.542}, {'end': 1868.404, 'text': "And heck, maybe there's something already here.", 'start': 1866.702, 'duration': 1.702}, {'end': 1871.647, 'text': "But there's plenty of other options for where this thing can go.", 'start': 1868.784, 'duration': 2.863}, {'end': 1876.171, 'text': 'And suppose that for the sake of discussion, the first available spot for the next number happens to be over here.', 'start': 1871.707, 'duration': 4.464}, {'end': 1880.895, 'text': 'at location 0x456 for the sake of discussion.', 'start': 1876.872, 'duration': 4.023}, {'end': 1883.197, 'text': "So that's where I'm going to plop the number 2.", 'start': 1881.215, 'duration': 1.982}, {'end': 1884.998, 'text': "And where might the number 3 end up? Oh, I don't know.", 'start': 1883.197, 'duration': 1.801}], 'summary': 'Discussion about placing numbers at locations 0x123 and 0x456.', 'duration': 25.723, 'max_score': 1859.275, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU1859275.jpg'}, {'end': 1978.814, 'src': 'embed', 'start': 1943.805, 'weight': 2, 'content': [{'end': 1951.531, 'text': "So let me at least plan ahead, so that when I ask the computer, like malloc recall from last week, for some memory, I don't just ask it now for space,", 'start': 1943.805, 'duration': 7.726}, {'end': 1952.672, 'text': 'for just the number.', 'start': 1951.531, 'duration': 1.141}, {'end': 1959.857, 'text': 'Let me start getting into the habit of asking malloc for enough space for the number and a pointer to another such number.', 'start': 1953.112, 'duration': 6.745}, {'end': 1963.841, 'text': "So it's a little more aggressive of me to ask for more memory, but I'm kind of planning ahead.", 'start': 1959.937, 'duration': 3.904}, {'end': 1965.262, 'text': 'And here is an example of a trade-off.', 'start': 1963.881, 'duration': 1.381}, {'end': 1969.205, 'text': 'Almost any time in CS when you start using more space, you can save time.', 'start': 1965.662, 'duration': 3.543}, {'end': 1973.289, 'text': 'Or if you try to conserve space, you might have to lose time.', 'start': 1969.626, 'duration': 3.663}, {'end': 1975.21, 'text': "It's being that kind of trade-off there.", 'start': 1973.769, 'duration': 1.441}, {'end': 1978.814, 'text': 'So how might I solve this? Well, let me abstract this away.', 'start': 1975.291, 'duration': 3.523}], 'summary': 'Planning ahead with memory allocation for trade-offs in computer science.', 'duration': 35.009, 'max_score': 1943.805, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU1943805.jpg'}, {'end': 2166.748, 'src': 'embed', 'start': 2138.293, 'weight': 3, 'content': [{'end': 2143.115, 'text': 'by just storing not just the numbers like 1,, 2, 3, but twice as much data,', 'start': 2138.293, 'duration': 4.822}, {'end': 2147.798, 'text': 'so that you have little breadcrumbs in the form of pointers that can lead you from one to the next.', 'start': 2143.115, 'duration': 4.683}, {'end': 2156.623, 'text': 'Any questions on these linked lists? Any questions? No? All right.', 'start': 2149.079, 'duration': 7.544}, {'end': 2157.283, 'text': 'Oh, yeah, over here.', 'start': 2156.703, 'duration': 0.58}, {'end': 2166.748, 'text': 'This does take more memory than an array because I now need space for these pointers.', 'start': 2162.827, 'duration': 3.921}], 'summary': 'Storing twice as much data with pointers in linked lists increases memory usage.', 'duration': 28.455, 'max_score': 2138.293, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU2138293.jpg'}, {'end': 2313.929, 'src': 'heatmap', 'start': 2233.57, 'weight': 0.803, 'content': [{'end': 2240.616, 'text': 'The compiler, essentially, will also help keep track of which values are valid or not inside of the stack.', 'start': 2233.57, 'duration': 7.046}, {'end': 2243.678, 'text': "Or really, the underlying code that you've written will keep track of that for you.", 'start': 2240.676, 'duration': 3.002}, {'end': 2246.12, 'text': "So it's managed for you at that point.", 'start': 2243.738, 'duration': 2.382}, {'end': 2247.809, 'text': 'All right, good question.', 'start': 2247.028, 'duration': 0.781}, {'end': 2249.289, 'text': 'Sorry it took me a bit to catch on.', 'start': 2247.849, 'duration': 1.44}, {'end': 2251.711, 'text': "So let's now translate this to actual code.", 'start': 2249.69, 'duration': 2.021}, {'end': 2255.273, 'text': "How could we implement this idea of, let's call these things nodes.", 'start': 2251.771, 'duration': 3.502}, {'end': 2256.654, 'text': "And that's a term of R and CS.", 'start': 2255.313, 'duration': 1.341}, {'end': 2263.378, 'text': 'Whenever you have some kind of data structure that encapsulates information, node, N-O-D-E, is the generic term for that.', 'start': 2256.694, 'duration': 6.684}, {'end': 2265.039, 'text': 'So each of these might be said to be a node.', 'start': 2263.418, 'duration': 1.621}, {'end': 2270.623, 'text': 'Well, how can we do this? Well, a couple of weeks ago, we saw how we could represent something like a student or a candidate.', 'start': 2265.34, 'duration': 5.283}, {'end': 2275.286, 'text': 'And a student, or rather a person, we said, well, has a name and a number.', 'start': 2271.003, 'duration': 4.283}, {'end': 2277.167, 'text': 'And we used a few pieces of syntax here.', 'start': 2275.506, 'duration': 1.661}, {'end': 2280.188, 'text': 'One, we used the struct keyword, which gives us a data structure.', 'start': 2277.367, 'duration': 2.821}, {'end': 2287.151, 'text': 'We used typedef, which defines the name person to be our new data type, representing that whole structure.', 'start': 2280.568, 'duration': 6.583}, {'end': 2291.794, 'text': 'So we probably have the right ingredients here to build up this thing called a node.', 'start': 2287.572, 'duration': 4.222}, {'end': 2298.036, 'text': "And just to be clear, what should go inside of one of these nodes, do we think? It's not going to be a name or a number, obviously.", 'start': 2292.234, 'duration': 5.802}, {'end': 2303.099, 'text': 'But what should a node have in terms of those fields, perhaps? Yeah.', 'start': 2298.137, 'duration': 4.962}, {'end': 2307.027, 'text': 'So a number and a pointer in some form.', 'start': 2304.286, 'duration': 2.741}, {'end': 2309.268, 'text': "So let's translate this to actual code.", 'start': 2307.047, 'duration': 2.221}, {'end': 2313.929, 'text': "So let's rename person to node to capture this notion here.", 'start': 2309.308, 'duration': 4.621}], 'summary': 'Compiler manages validity of values in stack. code translates to implementing nodes with number and pointer fields.', 'duration': 80.359, 'max_score': 2233.57, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU2233570.jpg'}], 'start': 1593.677, 'title': 'Memory management and linked lists', 'summary': "Delves into memory management in c, introducing syntax for custom data structures and explaining pointers' role in optimizing memory usage. it explores the trade-off between space and time efficiency, ultimately introducing linked lists as a solution. additionally, it discusses creating linked lists in memory, covering the storage of numbers and pointers, the use of memory addresses, the significance of null character, and a comparison of memory usage between arrays and pointers in c programming.", 'chapters': [{'end': 1978.814, 'start': 1593.677, 'title': 'Memory management and linked lists', 'summary': 'Discusses memory management in c, introducing new syntax for creating custom data structures and explaining how pointers can be used to optimize memory usage and efficiency, ultimately leading to the introduction of linked lists as a solution to memory allocation and management, with a trade-off between space and time efficiency.', 'duration': 385.137, 'highlights': ['Introduction of new syntax for creating custom data structures The discussion introduces a new piece of syntax that builds on previous concepts, including struct and typedef, to enable the creation of custom data structures.', 'Explanation of pointers for optimizing memory usage The use of pointers is explained as a means to manipulate computer memory, allowing for more efficient data storage and access.', 'Introduction of linked lists as a solution to memory allocation and management The concept of linked lists is introduced as a solution to memory management, allowing for dynamic allocation of memory and efficient data storage, albeit with a trade-off between space and time efficiency.']}, {'end': 2429.452, 'start': 1979.194, 'title': 'Creating linked lists in memory', 'summary': 'Discusses the concept of creating linked lists in memory by storing numbers and pointers, explaining the use of memory addresses, the significance of null character, the comparison of memory usage between arrays and pointers, and the implementation of nodes in c programming.', 'duration': 450.258, 'highlights': ['The significance of using memory addresses and pointers to stitch together a linked list of numbers, using twice as much data to refer to the next number.', "Explaining the significance of the null character (0x0) as a sentinel value to indicate the end of the list, preventing accidental probability of infinite loops, and the need to remember the list's starting point to detect cycles.", 'Comparison of memory usage between arrays and pointers, discussing the use of 8 bytes or 64 bits for pointers and the resulting increase in memory space.', 'Explanation of how malloc keeps track of valid memory addresses and the role of the compiler in managing valid values within the stack.', "Implementation of nodes in C programming, using the 'struct node' workaround to define the data structure and the use of 'struct node star' to represent pointers within the structure."]}], 'duration': 835.775, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU1593677.jpg', 'highlights': ['Introduction of linked lists as a solution to memory allocation and management', 'Explanation of pointers for optimizing memory usage', 'Introduction of new syntax for creating custom data structures', 'Comparison of memory usage between arrays and pointers', 'The significance of using memory addresses and pointers to stitch together a linked list of numbers', 'Explaining the significance of the null character (0x0) as a sentinel value to indicate the end of the list', "Implementation of nodes in C programming, using the 'struct node' workaround to define the data structure"]}, {'end': 3166.06, 'segs': [{'end': 2815.283, 'src': 'heatmap', 'start': 2550.279, 'weight': 0, 'content': [{'end': 2553.962, 'text': "But we'll see in a bit just what some of those trade-offs actually are.", 'start': 2550.279, 'duration': 3.683}, {'end': 2562.147, 'text': "All right, so from here, if we go back to the structure in code as we left it, let's start to now build up a linked list with some actual code.", 'start': 2554.522, 'duration': 7.625}, {'end': 2569.211, 'text': 'How do you go about in C representing a linked list in code? Well, at the moment, it would actually be as simple as this.', 'start': 2562.507, 'duration': 6.704}, {'end': 2575.295, 'text': 'You declare a variable called list, for instance, that itself stores the address of a node.', 'start': 2569.331, 'duration': 5.964}, {'end': 2577.476, 'text': "That's what node star means, the address of a node.", 'start': 2575.475, 'duration': 2.001}, {'end': 2582.779, 'text': 'So if you want to store a linked list in memory, You just create a variable called list or whatever else.', 'start': 2577.856, 'duration': 4.923}, {'end': 2588.701, 'text': 'And you just say that this variable is going to be pointing at the first node in the list, wherever it happens to end up.', 'start': 2583.199, 'duration': 5.502}, {'end': 2596.363, 'text': 'Because malloc is ultimately going to be the tool that we use just to go get at any one particular node in memory.', 'start': 2589.161, 'duration': 7.202}, {'end': 2598.844, 'text': "All right, so let's actually do this in pictorial form.", 'start': 2596.383, 'duration': 2.461}, {'end': 2606.907, 'text': 'When you write a line of code, like I just did here and I do not initialize it to anything with the assignment operator, an equal sign,', 'start': 2599.424, 'duration': 7.483}, {'end': 2610.991, 'text': "It does exist in memory as a box, as I'll draw it here called list.", 'start': 2607.507, 'duration': 3.484}, {'end': 2613.935, 'text': "But I've deliberately drawn Oscar inside of it.", 'start': 2611.432, 'duration': 2.503}, {'end': 2618.3, 'text': "Why? To connote what exactly? It's a garbage value.", 'start': 2614.015, 'duration': 4.285}, {'end': 2619.161, 'text': "It's a garbage value.", 'start': 2618.4, 'duration': 0.761}, {'end': 2627.703, 'text': 'variable in memory called list, which is going to give me 64 bits or 8 bytes somewhere drawn here with this box.', 'start': 2620.718, 'duration': 6.985}, {'end': 2634.867, 'text': "But if I myself have not used the assignment operator, it's not going to get magically initialized to any particular address for me.", 'start': 2628.023, 'duration': 6.844}, {'end': 2636.669, 'text': "It's not going to even give me a node.", 'start': 2634.887, 'duration': 1.782}, {'end': 2641.312, 'text': 'This is literally just going to be an address of a future node that exists.', 'start': 2637.029, 'duration': 4.283}, {'end': 2647.615, 'text': "So what would be a solution here? Suppose that I'm beginning to create my linked list, but I don't have any nodes yet.", 'start': 2641.812, 'duration': 5.803}, {'end': 2650.317, 'text': 'What would be a sensible thing to initialize?', 'start': 2648.016, 'duration': 2.301}, {'end': 2653.439, 'text': 'list 2, perhaps? Yeah, again?', 'start': 2650.317, 'duration': 3.122}, {'end': 2655.52, 'text': 'So just null, right?', 'start': 2654.6, 'duration': 0.92}, {'end': 2659.042, 'text': "When in doubt with pointers generally, it's a good thing to initialize things to null.", 'start': 2655.58, 'duration': 3.462}, {'end': 2660.683, 'text': "So at least it's not a garbage value.", 'start': 2659.082, 'duration': 1.601}, {'end': 2661.884, 'text': "It's a known value.", 'start': 2660.723, 'duration': 1.161}, {'end': 2666.567, 'text': "Invalid, yes, but it's a special value you can then check for with a conditional or the like.", 'start': 2662.044, 'duration': 4.523}, {'end': 2674.33, 'text': "So this might be a better way to create a linked list even before you've inserted any numbers into the thing itself.", 'start': 2666.607, 'duration': 7.723}, {'end': 2679.672, 'text': 'All right, so after that, how can we go about adding something to this linked list? So now the story looks like this.', 'start': 2674.891, 'duration': 4.781}, {'end': 2683.814, 'text': "Oscar is gone, because inside of this box is all 0 bits, just because it's nice and clean.", 'start': 2679.812, 'duration': 4.002}, {'end': 2686.195, 'text': 'And this represents an empty linked list.', 'start': 2684.294, 'duration': 1.901}, {'end': 2690.876, 'text': 'Well, if I want to add the number 1 to this linked list, what could I do??', 'start': 2686.775, 'duration': 4.101}, {'end': 2694.798, 'text': 'Well, perhaps I could start with code like this, borrowing inspiration from last week.', 'start': 2691.417, 'duration': 3.381}, {'end': 2699.199, 'text': "Let's ask malloc for enough space for the size of a node.", 'start': 2694.878, 'duration': 4.321}, {'end': 2704.981, 'text': "And this kind of gets to your question earlier, like, what is it I'm manipulating here? I don't just need space for an int.", 'start': 2699.599, 'duration': 5.382}, {'end': 2706.842, 'text': "And I don't just need space for a pointer.", 'start': 2705.341, 'duration': 1.501}, {'end': 2707.942, 'text': 'I need space for both.', 'start': 2706.962, 'duration': 0.98}, {'end': 2709.463, 'text': 'And I gave that thing a name.', 'start': 2708.002, 'duration': 1.461}, {'end': 2715.266, 'text': 'node So size of node figures out and does the arithmetic for me and gives me back the right number of bytes.', 'start': 2710.183, 'duration': 5.083}, {'end': 2723.412, 'text': "This then stores the address of that chunk of memory in what I'll temporarily called n, just to represent a generic new node.", 'start': 2716.047, 'duration': 7.365}, {'end': 2731.097, 'text': "And it's of type node star, because, just like last week when I asked malloc for enough space for an int and I stored it in an int star pointer,", 'start': 2723.912, 'duration': 7.185}, {'end': 2735.8, 'text': "this week if I'm asking for memory for a node, I'm storing it in a node star pointer.", 'start': 2731.097, 'duration': 4.703}, {'end': 2737.501, 'text': 'So technically nothing new there.', 'start': 2735.98, 'duration': 1.521}, {'end': 2741.404, 'text': 'except for this new term of art and data structure called node.', 'start': 2738.181, 'duration': 3.223}, {'end': 2745.948, 'text': 'All right, so what does that do for me? It essentially draws a picture like this in memory.', 'start': 2741.824, 'duration': 4.124}, {'end': 2751.813, 'text': "I still have my list variable from my previous line of code initialized to null, and that's why I've drawn it blank.", 'start': 2746.408, 'duration': 5.405}, {'end': 2760.058, 'text': 'I also now have a temporary variable called n, which I initialized to the return value of malloc, which gave me one of these nodes in memory.', 'start': 2752.374, 'duration': 7.684}, {'end': 2764.04, 'text': "But I've drawn it having garbage values, too, because I don't know what int is there.", 'start': 2760.118, 'duration': 3.922}, {'end': 2765.66, 'text': "I don't know what pointer is there.", 'start': 2764.44, 'duration': 1.22}, {'end': 2769.882, 'text': "It's garbage values, because malloc does not magically initialize memory for me.", 'start': 2765.72, 'duration': 4.162}, {'end': 2771.603, 'text': 'There is another function for that.', 'start': 2770.302, 'duration': 1.301}, {'end': 2774.384, 'text': 'But malloc alone just says, sure, use this chunk of memory.', 'start': 2771.903, 'duration': 2.481}, {'end': 2775.785, 'text': 'Deal with whatever is there.', 'start': 2774.804, 'duration': 0.981}, {'end': 2785.922, 'text': 'So how could I go about initializing this to known values? Well, suppose I want to insert the number 1 and then leave it at that, a list of size 1.', 'start': 2776.565, 'duration': 9.357}, {'end': 2786.944, 'text': 'I could do something like this.', 'start': 2785.922, 'duration': 1.022}, {'end': 2790.093, 'text': 'And this is where you have to think back to some of these basics.', 'start': 2787.932, 'duration': 2.161}, {'end': 2794.795, 'text': 'My conditional here is asking the question if n does not equal null.', 'start': 2790.653, 'duration': 4.142}, {'end': 2801.457, 'text': "so that is if malloc gave me valid memory and I don't have to quit altogether because my computer's out of memory.", 'start': 2794.795, 'duration': 6.662}, {'end': 2805.279, 'text': 'if n does not equal null, that is, it equals a valid address.', 'start': 2801.457, 'duration': 3.822}, {'end': 2806.339, 'text': "I'm going to go ahead and do this.", 'start': 2805.279, 'duration': 1.06}, {'end': 2808.78, 'text': 'And this is cryptic-looking syntax now.', 'start': 2806.499, 'duration': 2.281}, {'end': 2815.283, 'text': 'But does someone want to take a stab at translating this inside line of code to English?', 'start': 2809.52, 'duration': 5.763}], 'summary': 'Creating and initializing a linked list in c using malloc and pointers.', 'duration': 265.004, 'max_score': 2550.279, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU2550279.jpg'}, {'end': 2960.569, 'src': 'embed', 'start': 2931.03, 'weight': 1, 'content': [{'end': 2932.871, 'text': 'And again, this is just doing some nice bookkeeping.', 'start': 2931.03, 'duration': 1.841}, {'end': 2939.336, 'text': "Technically speaking, we might not need to set this to null if we're going to keep adding more and more numbers to it.", 'start': 2933.312, 'duration': 6.024}, {'end': 2945.62, 'text': "But I'm doing it step by step so that I have a very clean picture and there's no bugs in my code at this point.", 'start': 2939.376, 'duration': 6.244}, {'end': 2947.541, 'text': "But I'm still not done.", 'start': 2946.5, 'duration': 1.041}, {'end': 2949.882, 'text': "There's one last thing I'm going to have to do here.", 'start': 2947.881, 'duration': 2.001}, {'end': 2960.569, 'text': "If the goal ultimately was to insert the number 1 into my linked list, what's the last step I should perhaps do here? Just in English is fine.", 'start': 2950.483, 'duration': 10.086}], 'summary': 'Step-by-step bookkeeping for linked list insertion.', 'duration': 29.539, 'max_score': 2931.03, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU2931030.jpg'}], 'start': 2434.617, 'title': 'Memory allocation in data structures', 'summary': 'Discusses the use of struct node star pointer over int star pointer, emphasizing memory implications, including differences in memory consumption between arrays and pointers, and the impact on speed and efficiency of memory allocation.', 'chapters': [{'end': 2549.199, 'start': 2434.617, 'title': 'Memory allocation in data structures', 'summary': 'Discusses why a struct node star pointer is used instead of an int star pointer, emphasizing the need to point at the whole data structure and the implications on memory usage, including the difference in memory consumption between copying arrays and pointers, and the impact on speed and efficiency of memory allocation.', 'duration': 114.582, 'highlights': ["The need to point at the whole data structure in memory is emphasized, as it contains both a number and another pointer, impacting the compiler's understanding and memory allocation.", 'The memory usage implications between copying arrays and pointers are explained, highlighting the differences in memory consumption and the impact on speed and efficiency of memory allocation.', 'The difference in memory consumption between copying arrays and pointers is emphasized, with the additional note that pointers are 8 bytes compared to the typical 4 bytes for an integer.']}, {'end': 3166.06, 'start': 2549.219, 'title': 'Creating linked lists in c', 'summary': 'Explains how to represent and build a linked list in c, initializing variables, allocating memory, and updating the linked list, requiring a known value to represent the linked list and adding numbers to it.', 'duration': 616.841, 'highlights': ['Initializing a linked list in C involves declaring a variable to store the address of a node, which can be represented by a pointer called list, and initializing it to null for a clean picture. Declaring a variable to store the address of a node in C entails using a pointer (e.g., list) and initializing it to null, providing a clean representation of an empty linked list.', 'Allocating memory for a node in C using malloc requires considering the space for both an integer and a pointer, and this is achieved by storing the address of the allocated memory in a temporary pointer variable (e.g., n) of type node star. Allocating memory for a node in C using malloc necessitates considering the space for both an integer and a pointer, which is achieved by storing the address of the allocated memory in a temporary pointer variable (e.g., n) of type node star.', 'Updating the linked list in C involves setting the number field of the new node and initializing its next pointer to null, followed by updating the variable representing the linked list to point at the new node. Updating the linked list in C entails setting the number field of the new node, initializing its next pointer to null, and updating the variable representing the linked list to point at the new node.']}], 'duration': 731.443, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU2434617.jpg', 'highlights': ['The memory usage implications between copying arrays and pointers are explained, highlighting the differences in memory consumption and the impact on speed and efficiency of memory allocation.', 'Allocating memory for a node in C using malloc necessitates considering the space for both an integer and a pointer, which is achieved by storing the address of the allocated memory in a temporary pointer variable (e.g., n) of type node star.', "The need to point at the whole data structure in memory is emphasized, as it contains both a number and another pointer, impacting the compiler's understanding and memory allocation."]}, {'end': 4625.611, 'segs': [{'end': 3355.944, 'src': 'heatmap', 'start': 3187.37, 'weight': 0.918, 'content': [{'end': 3190.431, 'text': "I'm just going to quit out of this program because there's nothing useful to be done.", 'start': 3187.37, 'duration': 3.061}, {'end': 3191.332, 'text': 'at this point.', 'start': 3190.811, 'duration': 0.521}, {'end': 3193.774, 'text': 'But most likely, my computer is not going to run out of memory.', 'start': 3191.432, 'duration': 2.342}, {'end': 3196.717, 'text': "So I'm going to assume we can keep going with some of the logic here.", 'start': 3194.195, 'duration': 2.522}, {'end': 3203.564, 'text': "If n does not equal null, and that is it's a valid memory address, I'm going to say n bracket.", 'start': 3197.518, 'duration': 6.046}, {'end': 3205.206, 'text': "And I'm going to build this up backwards.", 'start': 3203.584, 'duration': 1.622}, {'end': 3206.387, 'text': "Well, let's do.", 'start': 3205.526, 'duration': 0.861}, {'end': 3208.002, 'text': "That's OK.", 'start': 3207.602, 'duration': 0.4}, {'end': 3208.763, 'text': "Let's go ahead and do this.", 'start': 3208.022, 'duration': 0.741}, {'end': 3211.326, 'text': 'n bracket number equals 1.', 'start': 3209.003, 'duration': 2.323}, {'end': 3215.73, 'text': 'And then n bracket or arrow next equals null.', 'start': 3211.326, 'duration': 4.404}, {'end': 3220.975, 'text': 'And now update list to point to new node.', 'start': 3216.31, 'duration': 4.665}, {'end': 3222.176, 'text': 'List equals n.', 'start': 3221.335, 'duration': 0.841}, {'end': 3229.402, 'text': "So at this point in the story, we've essentially constructed what was that first picture, which looks like this.", 'start': 3223.197, 'duration': 6.205}, {'end': 3234.185, 'text': 'This is the corresponding code via which we built up this node in memory.', 'start': 3229.882, 'duration': 4.303}, {'end': 3237.248, 'text': 'Suppose now we want to add the number 2 to the list.', 'start': 3234.626, 'duration': 2.622}, {'end': 3238.249, 'text': "So let's do this again.", 'start': 3237.328, 'duration': 0.921}, {'end': 3239.71, 'text': 'Add number.', 'start': 3238.269, 'duration': 1.441}, {'end': 3242.872, 'text': 'a number to list.', 'start': 3241.511, 'duration': 1.361}, {'end': 3248.394, 'text': "How might I do this? Well, I don't need to redeclare n because I can use the same temporary variables before.", 'start': 3243.212, 'duration': 5.182}, {'end': 3253.396, 'text': "So this time I'm just going to say n equals malloc and the size of a node.", 'start': 3248.594, 'duration': 4.802}, {'end': 3255.597, 'text': "I'm again going to have my safety check.", 'start': 3254.156, 'duration': 1.441}, {'end': 3259.779, 'text': "So if n equals equals null, then let's just quit out of this altogether.", 'start': 3255.617, 'duration': 4.162}, {'end': 3263.06, 'text': 'But, but, but, I have to be a little more careful now.', 'start': 3259.859, 'duration': 3.201}, {'end': 3268.783, 'text': 'Technically speaking, what do I still need to do before I quit out of my program?', 'start': 3264.541, 'duration': 4.242}, {'end': 3269.683, 'text': 'to be really proper?', 'start': 3268.783, 'duration': 0.9}, {'end': 3274.193, 'text': 'free the memory that did succeed a little higher up.', 'start': 3271.291, 'duration': 2.902}, {'end': 3279.315, 'text': 'So I think it suffices to free what is now called list way at the top.', 'start': 3274.373, 'duration': 4.942}, {'end': 3287.079, 'text': "All right, now if all was well, though, let's go ahead and say n bracket number equals 2.", 'start': 3280.036, 'duration': 7.043}, {'end': 3292.182, 'text': 'And now n bracket, or sorry, n arrow next equals null.', 'start': 3287.079, 'duration': 5.103}, {'end': 3303.688, 'text': "And now let's go ahead and add it to the list if I go ahead and do List arrow next equals n.", 'start': 3292.542, 'duration': 11.146}, {'end': 3312.511, 'text': "I think what we've just done is build up the equivalent now of this in the computer's memory by going to the list field's next field,", 'start': 3303.688, 'duration': 8.823}, {'end': 3319.794, 'text': "which is synonymous with the one node's bottom most box, and store the address of what was n, which a moment ago looked like this", 'start': 3312.511, 'duration': 7.283}, {'end': 3322.935, 'text': "And I'm just throwing away in the picture the temporary variable.", 'start': 3320.014, 'duration': 2.921}, {'end': 3324.576, 'text': 'All right, one last thing to do.', 'start': 3323.215, 'duration': 1.361}, {'end': 3330.779, 'text': 'Let me go down here and say, add a number to list, n equals malloc.', 'start': 3325.396, 'duration': 5.383}, {'end': 3331.66, 'text': "Let's do it one more time.", 'start': 3330.799, 'duration': 0.861}, {'end': 3332.86, 'text': 'Size of node.', 'start': 3331.74, 'duration': 1.12}, {'end': 3339.324, 'text': "And clearly, in a real program, we might want to start using a loop and do this dynamically or a function, because it's a lot of repetition now.", 'start': 3332.9, 'duration': 6.424}, {'end': 3342.406, 'text': 'But just to go through the syntax here, this is fine.', 'start': 3339.785, 'duration': 2.621}, {'end': 3347.149, 'text': "If n equals equals null, out of memory for some reason, let's return 1.", 'start': 3342.906, 'duration': 4.243}, {'end': 3355.944, 'text': 'But, but, but, we should return, we should free the list itself, and even the second node, list bracket next.', 'start': 3347.149, 'duration': 8.795}], 'summary': 'Demonstration of constructing a linked list in memory using c programming language.', 'duration': 168.574, 'max_score': 3187.37, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU3187370.jpg'}, {'end': 3347.149, 'src': 'embed', 'start': 3320.014, 'weight': 0, 'content': [{'end': 3322.935, 'text': "And I'm just throwing away in the picture the temporary variable.", 'start': 3320.014, 'duration': 2.921}, {'end': 3324.576, 'text': 'All right, one last thing to do.', 'start': 3323.215, 'duration': 1.361}, {'end': 3330.779, 'text': 'Let me go down here and say, add a number to list, n equals malloc.', 'start': 3325.396, 'duration': 5.383}, {'end': 3331.66, 'text': "Let's do it one more time.", 'start': 3330.799, 'duration': 0.861}, {'end': 3332.86, 'text': 'Size of node.', 'start': 3331.74, 'duration': 1.12}, {'end': 3339.324, 'text': "And clearly, in a real program, we might want to start using a loop and do this dynamically or a function, because it's a lot of repetition now.", 'start': 3332.9, 'duration': 6.424}, {'end': 3342.406, 'text': 'But just to go through the syntax here, this is fine.', 'start': 3339.785, 'duration': 2.621}, {'end': 3347.149, 'text': "If n equals equals null, out of memory for some reason, let's return 1.", 'start': 3342.906, 'duration': 4.243}], 'summary': 'Demonstrating dynamic memory allocation and error handling using malloc and if statement.', 'duration': 27.135, 'max_score': 3320.014, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU3320014.jpg'}, {'end': 3499.329, 'src': 'embed', 'start': 3467.668, 'weight': 2, 'content': [{'end': 3471.01, 'text': "But that's the kind of thing one needs to be careful about when touching memory at all.", 'start': 3467.668, 'duration': 3.342}, {'end': 3473.471, 'text': "You cannot touch memory after you've freed it.", 'start': 3471.07, 'duration': 2.401}, {'end': 3474.932, 'text': 'But here is my last step.', 'start': 3473.811, 'duration': 1.121}, {'end': 3481.252, 'text': 'Let me go ahead and update the number field of next to a number field of n to be 3.', 'start': 3475.572, 'duration': 5.68}, {'end': 3483.714, 'text': 'the next node of n to be null.', 'start': 3481.252, 'duration': 2.462}, {'end': 3491.822, 'text': 'And then just like in the slide earlier, I think I can do list next next equals n.', 'start': 3484.115, 'duration': 7.707}, {'end': 3499.329, 'text': "And that has the effect now of building up in the computer's memory essentially this data structure, very manually, very pedantically.", 'start': 3491.822, 'duration': 7.507}], 'summary': 'Updating memory, avoiding freed memory, and building data structure manually.', 'duration': 31.661, 'max_score': 3467.668, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU3467668.jpg'}, {'end': 3762.576, 'src': 'embed', 'start': 3729.87, 'weight': 4, 'content': [{'end': 3731.631, 'text': 'Then I update temp to point here.', 'start': 3729.87, 'duration': 1.761}, {'end': 3733.432, 'text': 'Then I update temp to point here.', 'start': 3731.871, 'duration': 1.561}, {'end': 3734.913, 'text': 'Then I update temp to point here.', 'start': 3733.732, 'duration': 1.181}, {'end': 3735.573, 'text': "Wait, that's null.", 'start': 3734.953, 'duration': 0.62}, {'end': 3737.174, 'text': 'The for loop ends.', 'start': 3736.053, 'duration': 1.121}, {'end': 3747.747, 'text': "So again, admittedly, much more cryptic than our familiar int i equals 0 and so forth, but it's just a different utilization of the for loop syntax.", 'start': 3738.098, 'duration': 9.649}, {'end': 3756.568, 'text': "Yes? How does it happen that you're always Good question.", 'start': 3747.767, 'duration': 8.801}, {'end': 3762.576, 'text': "How is it that I'm actually printing numbers and not printing out addresses instead? The compiler is helping me here.", 'start': 3756.608, 'duration': 5.968}], 'summary': "Demonstrating a different utilization of the for loop syntax and the compiler's assistance in printing numbers instead of addresses.", 'duration': 32.706, 'max_score': 3729.87, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU3729870.jpg'}, {'end': 3992.868, 'src': 'heatmap', 'start': 3906.693, 'weight': 0.73, 'content': [{'end': 3909.375, 'text': 'While the list itself is not null.', 'start': 3906.693, 'duration': 2.682}, {'end': 3912.377, 'text': "so while there's a list to be freed, What do I want to do??", 'start': 3909.375, 'duration': 3.002}, {'end': 3915.719, 'text': "I'm going to give myself a temporary variable called temp again.", 'start': 3912.937, 'duration': 2.782}, {'end': 3917.961, 'text': "And it's a different temp because it's in a different scope.", 'start': 3915.78, 'duration': 2.181}, {'end': 3921.084, 'text': "It's inside of the while loop instead of the for loop a few lines earlier.", 'start': 3918.001, 'duration': 3.083}, {'end': 3929.411, 'text': 'I am going to initialize temp to be the address of the next node just so I can get one step ahead of things.', 'start': 3921.104, 'duration': 8.307}, {'end': 3936.396, 'text': 'Why am I doing this? Because now I can boldly free the list itself which does not mean the whole list.', 'start': 3929.851, 'duration': 6.545}, {'end': 3941.6, 'text': "Again, I'm freeing the address in list, which is the address of the number one node.", 'start': 3936.596, 'duration': 5.004}, {'end': 3942.881, 'text': "That's what list is.", 'start': 3942.021, 'duration': 0.86}, {'end': 3945.243, 'text': "It's just the address of the number one node.", 'start': 3942.941, 'duration': 2.302}, {'end': 3955.951, 'text': 'So if I first use temp to point at the number two slightly in the middle of the picture, then it is safe for me on line 61 at the moment to free list.', 'start': 3945.623, 'duration': 10.328}, {'end': 3958.073, 'text': 'that is the address of the first node.', 'start': 3955.951, 'duration': 2.122}, {'end': 3966.97, 'text': "Now I'm going to say, all right, once I freed the first node in the list, I can update the list itself to be literally temp.", 'start': 3958.673, 'duration': 8.297}, {'end': 3969.317, 'text': 'And now the loop repeats.', 'start': 3967.836, 'duration': 1.481}, {'end': 3978.041, 'text': "So what's happening here, if you think about this picture, temp is initially pointing at not the list, but list arrow next.", 'start': 3969.817, 'duration': 8.224}, {'end': 3981.202, 'text': 'So temp, represented by my right hand here, is pointing at the number two.', 'start': 3978.141, 'duration': 3.061}, {'end': 3987.485, 'text': 'Totally safe and reasonable to free now the list itself, AKA the address of the number one node.', 'start': 3981.683, 'duration': 5.802}, {'end': 3992.868, 'text': 'That has the effect of just throwing away the number one node, telling the computer, you can reuse that memory for you.', 'start': 3987.805, 'duration': 5.063}], 'summary': 'In the code, the list is freed by updating the list itself to the address of the next node, allowing memory to be reused.', 'duration': 86.175, 'max_score': 3906.693, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU3906693.jpg'}, {'end': 3981.202, 'src': 'embed', 'start': 3958.673, 'weight': 3, 'content': [{'end': 3966.97, 'text': "Now I'm going to say, all right, once I freed the first node in the list, I can update the list itself to be literally temp.", 'start': 3958.673, 'duration': 8.297}, {'end': 3969.317, 'text': 'And now the loop repeats.', 'start': 3967.836, 'duration': 1.481}, {'end': 3978.041, 'text': "So what's happening here, if you think about this picture, temp is initially pointing at not the list, but list arrow next.", 'start': 3969.817, 'duration': 8.224}, {'end': 3981.202, 'text': 'So temp, represented by my right hand here, is pointing at the number two.', 'start': 3978.141, 'duration': 3.061}], 'summary': 'Updating list to temp after freeing first node, pointing at number two.', 'duration': 22.529, 'max_score': 3958.673, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU3958673.jpg'}, {'end': 4501.918, 'src': 'embed', 'start': 4471.847, 'weight': 1, 'content': [{'end': 4476.989, 'text': "The moment you point temporarily, if you could, to Lauren, I have no idea where he's pointing to.", 'start': 4471.847, 'duration': 5.142}, {'end': 4481.65, 'text': 'I have no idea how to get back to Caleb or Hannah or anyone else on stage.', 'start': 4477.049, 'duration': 4.601}, {'end': 4482.53, 'text': 'So that was bad.', 'start': 4481.91, 'duration': 0.62}, {'end': 4483.63, 'text': 'So you did undo it.', 'start': 4482.61, 'duration': 1.02}, {'end': 4484.331, 'text': "So that's good.", 'start': 4483.83, 'duration': 0.501}, {'end': 4486.791, 'text': 'I think we need Lauren to make a decision first.', 'start': 4484.991, 'duration': 1.8}, {'end': 4492.153, 'text': "Who should you point at? So pointing at Caleb, why? Because you're pointing at literally who Pedro is pointing at.", 'start': 4486.851, 'duration': 5.302}, {'end': 4496.134, 'text': 'Pedro, now what are you safe to do? Good, so order of operations there matters.', 'start': 4492.213, 'duration': 3.921}, {'end': 4501.918, 'text': "And if we had just done this line of code in red here, list equals in, that was like Pedro's first instinct.", 'start': 4496.194, 'duration': 5.724}], 'summary': "Confusion on pointing, but pedro's safe move worked.", 'duration': 30.071, 'max_score': 4471.847, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU4471847.jpg'}], 'start': 3166.74, 'title': 'Linked lists in c', 'summary': 'Covers adding numbers to a list in memory, manipulating linked lists, freeing linked lists, dynamic memory allocation, and maintaining sorted order to avoid memory leaks, with emphasis on safety, memory allocation, and traversal.', 'chapters': [{'end': 3242.872, 'start': 3166.74, 'title': 'Adding numbers to list', 'summary': 'Discusses the process of adding numbers to a list in memory using malloc and pointers, ensuring the safety of memory allocation and updating the list to point to the new node.', 'duration': 76.132, 'highlights': ['The chapter explains the process of adding a number to a list using malloc to allocate memory for a new node.', 'It emphasizes the importance of a safety check to ensure the validity of the memory address and the availability of memory before proceeding with the logic.', 'The chapter illustrates the process of updating the list to point to the new node after adding the number.']}, {'end': 3798.826, 'start': 3243.212, 'title': 'Manipulating linked lists in c', 'summary': 'Discusses memory allocation, proper freeing of memory, building a linked list, accessing linked list elements, and printing linked list elements using pointers and for loops in c.', 'duration': 555.614, 'highlights': ['Using malloc to allocate memory for a node and implementing proper safety checks, including handling out-of-memory errors', 'Freeing memory properly, including freeing the list and its subsequent nodes, and avoiding double-freeing', 'Building a linked list by connecting nodes and storing addresses', 'Explaining the need for a more dynamic approach using loops or functions instead of repetitive code', 'Highlighting the importance of proper memory management and avoiding accessing freed memory']}, {'end': 4138.412, 'start': 3799.206, 'title': 'Linked list freeing process', 'summary': 'Elaborates on the process of freeing a linked list through a while loop and the use of temporary variables, emphasizing the necessity to actively manage linked list memory allocation and traversal, and the introduction of these concepts in upcoming materials.', 'duration': 339.206, 'highlights': ['The chapter elaborates on the process of freeing a linked list. The chapter describes the process of freeing a linked list using a while loop and temporary variables, emphasizing the need for manual memory management with linked lists.', 'Emphasizes the necessity to actively manage linked list memory allocation and traversal. The discussion emphasizes the need for active management of linked list memory allocation and traversal, highlighting the difference from arrays and the manual control over memory allocation in linked lists.', 'Introduction of these concepts in upcoming materials. The chapter hints at the introduction of concepts related to linked list memory management in upcoming materials, indicating an opportunity to explore these ideas further in the context of problem set 5.']}, {'end': 4625.611, 'start': 4138.412, 'title': 'Linked lists and memory allocation', 'summary': 'Discusses linked lists, dynamic memory allocation, and the importance of maintaining sorted order to avoid memory leaks, with volunteers demonstrating the process of inserting elements into a linked list.', 'duration': 487.199, 'highlights': ['The chapter discusses linked lists and dynamic memory allocation. The discussion covers the use of arrow notation to walk down the arrows of a linked list and the automation of complexity in Python next week.', 'Volunteers demonstrate the process of inserting elements into a linked list, emphasizing the importance of maintaining sorted order to avoid memory leaks. Volunteers simulate the insertion of numbers and pointers into a linked list, highlighting the significance of maintaining sorted order to prevent memory leaks and the potential consequences of orphaning memory.', 'The instructor emphasizes maintaining sorted order and the consequences of orphaning memory. The instructor stresses the importance of maintaining sorted order in linked lists to avoid orphaning memory and discusses the potential slowdown of devices due to memory leaks.']}], 'duration': 1458.871, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU3166740.jpg', 'highlights': ['Emphasizes maintaining sorted order to avoid memory leaks', 'Explains adding numbers to a list using malloc for memory allocation', 'Illustrates updating the list to point to the new node after adding the number', 'Elaborates on freeing a linked list using a while loop and temporary variables', 'Stresses the importance of proper memory management and avoiding accessing freed memory', 'Describes the process of inserting elements into a linked list', 'Volunteers simulate the insertion of numbers and pointers into a linked list', 'Introduction of concepts related to linked list memory management in upcoming materials']}, {'end': 5432.437, 'segs': [{'end': 4812.646, 'src': 'embed', 'start': 4773.099, 'weight': 0, 'content': [{'end': 4776.201, 'text': "And so obviously, you're going to have to search all of the n elements.", 'start': 4773.099, 'duration': 3.102}, {'end': 4782.604, 'text': 'And I drew these things with boxes on top of them, because again, even though you and I can immediately see where the 5 is, for instance,', 'start': 4776.241, 'duration': 6.363}, {'end': 4786.806, 'text': 'the computer can only figure that out by starting at the beginning and going there.', 'start': 4782.604, 'duration': 4.202}, {'end': 4788.667, 'text': 'So there, too, is another trade-off.', 'start': 4787.146, 'duration': 1.521}, {'end': 4797.714, 'text': 'it would seem that overnight we have lost the ability to do a very powerful algorithm from week 0 known as binary search.', 'start': 4789.187, 'duration': 8.527}, {'end': 4798.414, 'text': "It's gone,", 'start': 4797.774, 'duration': 0.64}, {'end': 4806.781, 'text': "because there's no way in this picture to jump mathematically to the middle node unless you remember where it is and then remember where every other node is.", 'start': 4798.414, 'duration': 8.367}, {'end': 4808.282, 'text': "And at that point, you're back to an array.", 'start': 4806.801, 'duration': 1.481}, {'end': 4812.646, 'text': 'Link lists by design only remember the next node in the list.', 'start': 4808.783, 'duration': 3.863}], 'summary': 'Challenges of searching n elements with linked lists and loss of binary search algorithm.', 'duration': 39.547, 'max_score': 4773.099, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU4773099.jpg'}, {'end': 4888.678, 'src': 'embed', 'start': 4858.527, 'weight': 1, 'content': [{'end': 4864.491, 'text': 'At this point, though in the term, and really this point in the story, you should start to question these kinds of very simplistic questions,', 'start': 4858.527, 'duration': 5.964}, {'end': 4868.893, 'text': 'to be honest, because the answer is almost always going to depend.', 'start': 4864.491, 'duration': 4.402}, {'end': 4875.655, 'text': "If I've just got a linked list that looks like this, the first question back to someone asking this question would be well,", 'start': 4868.933, 'duration': 6.722}, {'end': 4877.315, 'text': 'does the list need to be sorted??', 'start': 4875.655, 'duration': 1.66}, {'end': 4880.376, 'text': "I've drawn it as sorted and it might imply as much.", 'start': 4877.715, 'duration': 2.661}, {'end': 4881.976, 'text': "So that's a reasonable assumption to have made.", 'start': 4880.396, 'duration': 1.58}, {'end': 4888.678, 'text': "But if I don't care about maintaining sorted order, I could actually insert into a linked list in constant time.", 'start': 4882.316, 'duration': 6.362}], 'summary': 'Question assumptions in coding; sorting impacts insertion time.', 'duration': 30.151, 'max_score': 4858.527, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU4858527.jpg'}, {'end': 5154.595, 'src': 'embed', 'start': 5125.826, 'weight': 5, 'content': [{'end': 5129.829, 'text': 'What if the data these nodes are storing are numbers, so still integers?', 'start': 5125.826, 'duration': 4.003}, {'end': 5139.438, 'text': 'But what if we kind of connected these cleverly like an old family tree? whereby every node has not one pointer now, but as many as two?', 'start': 5130.389, 'duration': 9.049}, {'end': 5142.682, 'text': 'Maybe 0, like in the leaves at the bottom there in green.', 'start': 5139.918, 'duration': 2.764}, {'end': 5147.787, 'text': 'But other nodes on the interior might have as many as two, like having two children, so to speak.', 'start': 5143.062, 'duration': 4.725}, {'end': 5149.81, 'text': 'And indeed, the vernacular here is exactly that.', 'start': 5147.807, 'duration': 2.003}, {'end': 5151.532, 'text': 'This would be called the root of the tree.', 'start': 5149.87, 'duration': 1.662}, {'end': 5154.595, 'text': 'Or this would be a parent with respect to these children.', 'start': 5152.052, 'duration': 2.543}], 'summary': 'Data nodes storing numbers connected in a family tree structure with varying number of pointers.', 'duration': 28.769, 'max_score': 5125.826, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU5125826.jpg'}], 'start': 4625.731, 'title': 'Programming challenges and data structures', 'summary': 'Discusses the challenges of navigating dense code and the importance of understanding higher level descriptions when programming, and explains the time complexity of operations on linked lists and introduces the concept of a binary search tree, highlighting its advantages and trade-offs in terms of time and space complexity.', 'chapters': [{'end': 4659.237, 'start': 4625.731, 'title': 'Programming at higher level', 'summary': 'Discusses the challenge of navigating dense code, emphasizing the importance of understanding higher level descriptions and the value of conversational insights when programming.', 'duration': 33.506, 'highlights': ['The importance of understanding higher level descriptions and the value of conversational insights when programming.', 'Navigating dense code and the challenge of losing sight of the forest for the trees.', 'The assumption that one can figure out how to implement a programming concept by referring to textbooks or class notes.']}, {'end': 5432.437, 'start': 4659.297, 'title': 'Data structures and binary search tree', 'summary': 'Explains the time complexity of operations on linked lists, including searching and inserting, and introduces the concept of a binary search tree, highlighting its advantages and trade-offs in terms of time and space complexity.', 'duration': 773.14, 'highlights': ['Binary search tree offers logarithmic time complexity for searching In a binary search tree, the worst-case time complexity for searching for an element is log base 2 of n, providing a significant improvement over the linear time complexity of linked lists.', 'Linked list insertion time complexity depends on maintaining sorted order For maintaining sorted order, linked list insertion has a time complexity of big O of n, but for non-sorted lists, it can be achieved in constant time, highlighting the trade-off between maintaining order and time complexity.', 'Trade-off between time and space complexity in binary search tree The binary search tree offers the advantage of logarithmic time complexity for searching but incurs the trade-off of requiring more space, as each node now needs not only a number but also two pointers, demonstrating the inherent trade-offs in data structure design.']}], 'duration': 806.706, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU4625731.jpg', 'highlights': ['Binary search tree offers logarithmic time complexity for searching, providing a significant improvement over the linear time complexity of linked lists.', 'The importance of understanding higher level descriptions and the value of conversational insights when programming.', 'Navigating dense code and the challenge of losing sight of the forest for the trees.', 'Linked list insertion time complexity depends on maintaining sorted order, highlighting the trade-off between maintaining order and time complexity.', 'Trade-off between time and space complexity in binary search tree, demonstrating the inherent trade-offs in data structure design.', 'The assumption that one can figure out how to implement a programming concept by referring to textbooks or class notes.']}, {'end': 5997.675, 'segs': [{'end': 5479.089, 'src': 'embed', 'start': 5450.232, 'weight': 3, 'content': [{'end': 5454.555, 'text': 'Let me go ahead here and let me just open a program I wrote here in advance.', 'start': 5450.232, 'duration': 4.323}, {'end': 5458.519, 'text': 'So let me, in a moment, copy over a file called tree.c.', 'start': 5454.635, 'duration': 3.884}, {'end': 5461.681, 'text': "which we'll have on the course's website.", 'start': 5460.12, 'duration': 1.561}, {'end': 5467.824, 'text': "And I'll walk you through some of the logic here that I've written for tree.c.", 'start': 5461.721, 'duration': 6.103}, {'end': 5474.927, 'text': 'All right, so what do we have here first? So here is a implementation of a binary search tree for numbers.', 'start': 5468.564, 'duration': 6.363}, {'end': 5479.089, 'text': "And as before, I've just kind of played around and I've inserted the numbers manually.", 'start': 5475.007, 'duration': 4.082}], 'summary': 'The speaker provides an implementation of a binary search tree for numbers and manually inserts the numbers into the tree.', 'duration': 28.857, 'max_score': 5450.232, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU5450232.jpg'}, {'end': 5593.891, 'src': 'heatmap', 'start': 5495.909, 'weight': 0, 'content': [{'end': 5498.41, 'text': 'and that also allow me to print the tree in order.', 'start': 5495.909, 'duration': 2.501}, {'end': 5506.713, 'text': "So, even though they're not sorted left to right I bet if I'm clever about what child I print first I can reconstruct the idea of printing this tree properly.", 'start': 5498.47, 'duration': 8.243}, {'end': 5510.695, 'text': "So how might I implement a binary search tree? Here's my main function.", 'start': 5507.353, 'duration': 3.342}, {'end': 5513.636, 'text': 'Here is how I might represent a tree of size 0.', 'start': 5511.175, 'duration': 2.461}, {'end': 5515.377, 'text': "It's just a null pointer called tree.", 'start': 5513.636, 'duration': 1.741}, {'end': 5518.525, 'text': "Here's how I might add a number to that list.", 'start': 5516.644, 'duration': 1.881}, {'end': 5524.929, 'text': 'So here, for instance, is me mallocing space for a node, storing it in a temporary variable called n.', 'start': 5518.645, 'duration': 6.284}, {'end': 5528.091, 'text': 'Here is me just doing a safety check, make sure n does not equal null.', 'start': 5524.929, 'duration': 3.162}, {'end': 5531.493, 'text': 'And then here is me initializing this node to contain the number 2 first.', 'start': 5528.491, 'duration': 3.002}, {'end': 5538.116, 'text': 'then initializing the left child of that node to be null and the right child of that node to be null,', 'start': 5532.834, 'duration': 5.282}, {'end': 5543.117, 'text': 'and then initializing the tree itself to be equal to that particular node.', 'start': 5538.116, 'duration': 5.001}, {'end': 5548.559, 'text': "So at this point in the story, there's just one rectangle on the screen containing the number 2 with no children.", 'start': 5543.137, 'duration': 5.422}, {'end': 5551.899, 'text': "All right, let's just add manually to this a little further.", 'start': 5549.399, 'duration': 2.5}, {'end': 5555.12, 'text': "Let's add another number to the list by mallocing another node.", 'start': 5552.3, 'duration': 2.82}, {'end': 5558.941, 'text': "I don't need to redeclare n as a node star because it already exists at this point.", 'start': 5555.42, 'duration': 3.521}, {'end': 5560.622, 'text': "Here's a little safety check.", 'start': 5559.342, 'duration': 1.28}, {'end': 5567.664, 'text': "I'm going to not bother with my, let me do this, free memory here just to be safe.", 'start': 5561.32, 'duration': 6.344}, {'end': 5573.829, 'text': "Do I want to do this? We're going to free memory 2, which I've not done here, but I'll save that for another time.", 'start': 5567.704, 'duration': 6.125}, {'end': 5576.651, 'text': "Here I'm going to initialize the number to 1.", 'start': 5574.349, 'duration': 2.302}, {'end': 5580.033, 'text': "I'm going to initialize the children of this no node to null and null.", 'start': 5576.651, 'duration': 3.382}, {'end': 5587.026, 'text': "And now I'm going to do this, initialize the tree's left child to be n.", 'start': 5580.822, 'duration': 6.204}, {'end': 5593.891, 'text': "So what that's essentially doing here is, if this is my root node, the single rectangle I described a moment ago, that currently has no children,", 'start': 5587.026, 'duration': 6.865}], 'summary': 'Implementing a binary search tree with nodes and pointers.', 'duration': 97.982, 'max_score': 5495.909, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU5495909.jpg'}, {'end': 5567.664, 'src': 'embed', 'start': 5538.116, 'weight': 2, 'content': [{'end': 5543.117, 'text': 'and then initializing the tree itself to be equal to that particular node.', 'start': 5538.116, 'duration': 5.001}, {'end': 5548.559, 'text': "So at this point in the story, there's just one rectangle on the screen containing the number 2 with no children.", 'start': 5543.137, 'duration': 5.422}, {'end': 5551.899, 'text': "All right, let's just add manually to this a little further.", 'start': 5549.399, 'duration': 2.5}, {'end': 5555.12, 'text': "Let's add another number to the list by mallocing another node.", 'start': 5552.3, 'duration': 2.82}, {'end': 5558.941, 'text': "I don't need to redeclare n as a node star because it already exists at this point.", 'start': 5555.42, 'duration': 3.521}, {'end': 5560.622, 'text': "Here's a little safety check.", 'start': 5559.342, 'duration': 1.28}, {'end': 5567.664, 'text': "I'm going to not bother with my, let me do this, free memory here just to be safe.", 'start': 5561.32, 'duration': 6.344}], 'summary': 'Creating a tree with one rectangle and adding another number using malloc.', 'duration': 29.548, 'max_score': 5538.116, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU5538116.jpg'}, {'end': 5714.11, 'src': 'embed', 'start': 5684.778, 'weight': 1, 'content': [{'end': 5688.98, 'text': 'Yeah, so this is actually perhaps the most compelling use of recursion yet.', 'start': 5684.778, 'duration': 4.202}, {'end': 5693.782, 'text': "It wasn't really that compelling with the Mario thing, because we had such an easy implementation with a for loop weeks ago.", 'start': 5689.04, 'duration': 4.742}, {'end': 5700.445, 'text': 'But here is kind of a perfect application of recursion, where your data structure itself is recursive.', 'start': 5694.302, 'duration': 6.143}, {'end': 5704.927, 'text': 'If you take any snip of any branch, it still looks like a tree, just a smaller one.', 'start': 5700.485, 'duration': 4.442}, {'end': 5706.648, 'text': 'That lends itself to recursion.', 'start': 5705.227, 'duration': 1.421}, {'end': 5714.11, 'text': 'So here is this leap of faith where I say, ah, print my left tree, or my left subtree, if you will, via my child at the left.', 'start': 5707.068, 'duration': 7.042}], 'summary': 'Recursion is a compelling approach for a recursive data structure like a tree.', 'duration': 29.332, 'max_score': 5684.778, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU5684778.jpg'}, {'end': 5852.74, 'src': 'embed', 'start': 5826.916, 'weight': 4, 'content': [{'end': 5831.942, 'text': "And what's even cooler here, relatively speaking, suppose we wanted to search something like this.", 'start': 5826.916, 'duration': 5.026}, {'end': 5836.207, 'text': 'Binary search actually gets pretty straightforward to implement, too.', 'start': 5832.322, 'duration': 3.885}, {'end': 5839.37, 'text': 'For instance, here might be the prototype for a search function.', 'start': 5836.287, 'duration': 3.083}, {'end': 5841.232, 'text': 'for a binary search tree.', 'start': 5840.071, 'duration': 1.161}, {'end': 5844.234, 'text': 'You give me the root of a tree.', 'start': 5841.652, 'duration': 2.582}, {'end': 5846.375, 'text': "And you give me a number I'm looking for.", 'start': 5844.654, 'duration': 1.721}, {'end': 5850.398, 'text': "And I can pretty easily now return true if it's in there or false if it's not.", 'start': 5846.475, 'duration': 3.923}, {'end': 5852.74, 'text': "How? Well, let's first ask a question.", 'start': 5850.458, 'duration': 2.282}], 'summary': 'Binary search makes searching straightforward, returning true or false for a given number.', 'duration': 25.824, 'max_score': 5826.916, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU5826916.jpg'}], 'start': 5432.497, 'title': 'Binary search tree implementation in c', 'summary': 'Covers the implementation of a binary search tree in c, including creation of nodes, insertion of numbers, tree structure, printing, freeing, and recursion, showcasing practical applications and elegance of recursion in data structure, with a reference to the use of true and false values in the standard bool library.', 'chapters': [{'end': 5639.095, 'start': 5432.497, 'title': 'Implementing a binary search tree in c', 'summary': 'Discusses the implementation of a binary search tree in c, covering the creation of nodes, insertion of numbers, and the structure of the resulting tree, ultimately resulting in a sorted data structure.', 'duration': 206.598, 'highlights': ['The code demonstrates the implementation of a binary search tree in C, including the creation of nodes and insertion of numbers, resulting in a sorted data structure.', 'The process involves dynamically allocating memory for nodes, initializing them with numbers, and linking them together to form the binary search tree.', 'The program successfully creates a binary search tree with the numbers 1, 2, and 3, demonstrating the functionality of the implemented code.']}, {'end': 5806.72, 'start': 5639.656, 'title': 'Printing and freeing binary tree', 'summary': 'Discusses the implementation of printing and freeing a binary tree using recursion, with emphasis on the base case and the order of recursive calls, showcasing the practical application of recursion in a data structure.', 'duration': 167.064, 'highlights': ['The print tree function recursively prints the left child, the root node, and the right child, demonstrating a practical application of recursion in a data structure.', 'The implementation of the print tree function highlights the base case, ensuring that the recursion does not continue infinitely and efficiently prints the elements of the tree.', 'The concept of reversing the order of the list in the tree is showcased, demonstrating the flexibility and practicality of the recursive approach in handling different tree traversal orders.', 'The free tree function recursively frees the left child, right child, and then the root, emphasizing the importance of the order of freeing operations to prevent memory leaks.']}, {'end': 5997.675, 'start': 5806.72, 'title': 'Binary search tree recursion', 'summary': 'Explains the concept of recursion in binary search tree implementation, including the search function prototype and the elegance of recursion in this context, with a reference to the use of true and false values in the standard bool library.', 'duration': 190.955, 'highlights': ['Recursion in binary search tree implementation The transcript discusses the example of recursion and the recursive use of an actual data structure.', 'Search function prototype for binary search tree The prototype for a search function for a binary search tree is presented, allowing for the easy implementation of searching for a specific number in the tree.', 'Use of true and false values in standard bool library The transcript explains the usage of true and false as values defined in the standard bool library, advising against explicit comparison to 0 and 1.']}], 'duration': 565.178, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU5432497.jpg', 'highlights': ['The program successfully creates a binary search tree with the numbers 1, 2, and 3, demonstrating the functionality of the implemented code.', 'The print tree function recursively prints the left child, the root node, and the right child, demonstrating a practical application of recursion in a data structure.', 'The concept of reversing the order of the list in the tree is showcased, demonstrating the flexibility and practicality of the recursive approach in handling different tree traversal orders.', 'The free tree function recursively frees the left child, right child, and then the root, emphasizing the importance of the order of freeing operations to prevent memory leaks.', 'Search function prototype for binary search tree The prototype for a search function for a binary search tree is presented, allowing for the easy implementation of searching for a specific number in the tree.', 'Use of true and false values in standard bool library The transcript explains the usage of true and false as values defined in the standard bool library, advising against explicit comparison to 0 and 1.', 'The process involves dynamically allocating memory for nodes, initializing them with numbers, and linking them together to form the binary search tree.', 'The implementation of the print tree function highlights the base case, ensuring that the recursion does not continue infinitely and efficiently prints the elements of the tree.', 'Recursion in binary search tree implementation The transcript discusses the example of recursion and the recursive use of an actual data structure.']}, {'end': 7034.597, 'segs': [{'end': 6214.08, 'src': 'embed', 'start': 6190.196, 'weight': 2, 'content': [{'end': 6198.122, 'text': "So unfortunately, the literal answer to the question here is, what's the running time of search, well, hopefully log n.", 'start': 6190.196, 'duration': 7.926}, {'end': 6200.485, 'text': "But not if you don't maintain the balance of the tree.", 'start': 6198.122, 'duration': 2.363}, {'end': 6207.773, 'text': 'Both insert and search could actually devolve into, instead of big O of log n, literally big O of n.', 'start': 6200.565, 'duration': 7.208}, {'end': 6214.08, 'text': "If you don't somehow take into account and we're not going to do the code for that here sort of a higher level thing you might explore down the road,", 'start': 6207.773, 'duration': 6.307}], 'summary': 'Search running time: ideally log n, but can devolve to o(n) without balanced tree maintenance.', 'duration': 23.884, 'max_score': 6190.196, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU6190196.jpg'}, {'end': 6372.96, 'src': 'embed', 'start': 6336.169, 'weight': 0, 'content': [{'end': 6338.771, 'text': 'exactly to the location that they need to go.', 'start': 6336.169, 'duration': 2.602}, {'end': 6342.814, 'text': "So for instance, here's our array, 0 index, 0 through 25.", 'start': 6339.131, 'duration': 3.683}, {'end': 6348.518, 'text': "If I think of this, though, as A through Z, I'm going to think of these 26 locations now in the context of a hash table,", 'start': 6342.814, 'duration': 5.704}, {'end': 6349.979, 'text': "as what we'll generally call buckets.", 'start': 6348.518, 'duration': 1.461}, {'end': 6352.221, 'text': 'So buckets into which you can put values.', 'start': 6350.239, 'duration': 1.982}, {'end': 6358.008, 'text': 'So for instance, suppose that we want to insert a value, one name, into this data structure.', 'start': 6352.602, 'duration': 5.406}, {'end': 6359.63, 'text': 'And that name is, say, Albus.', 'start': 6358.048, 'duration': 1.582}, {'end': 6361.452, 'text': 'So Albus starting with A.', 'start': 6359.87, 'duration': 1.582}, {'end': 6364.495, 'text': 'Albus might go at the very beginning of this list.', 'start': 6361.452, 'duration': 3.043}, {'end': 6364.996, 'text': 'All right.', 'start': 6364.816, 'duration': 0.18}, {'end': 6366.397, 'text': 'And we want to insert another name.', 'start': 6365.196, 'duration': 1.201}, {'end': 6368.878, 'text': 'This one happens to be Zacharias, starting with z.', 'start': 6366.437, 'duration': 2.441}, {'end': 6372.96, 'text': 'So it goes all the way at the end of this data structure in location 25, a.k.a.', 'start': 6368.878, 'duration': 4.082}], 'summary': 'Explaining the concept of hash tables and inserting values into buckets using an array of 26 locations.', 'duration': 36.791, 'max_score': 6336.169, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU6336169.jpg'}, {'end': 6621.232, 'src': 'heatmap', 'start': 6538.726, 'weight': 0.931, 'content': [{'end': 6542.429, 'text': "Well, how might we represent something like this? Here's how we could describe this thing.", 'start': 6538.726, 'duration': 3.703}, {'end': 6545.451, 'text': 'A node in the context of a linked list could be this.', 'start': 6542.869, 'duration': 2.582}, {'end': 6553.837, 'text': "I have an array called word of type char, and it's big enough to fit the longest word in the alphabet plus 1.", 'start': 6546.091, 'duration': 7.746}, {'end': 6557.066, 'text': 'And the plus 1, why, probably? the null character.', 'start': 6553.837, 'duration': 3.229}, {'end': 6563.292, 'text': "So I'm assuming that longest word is like a constant defined elsewhere in the story, and it's something big like 40, 100, whatever.", 'start': 6557.206, 'duration': 6.086}, {'end': 6570.058, 'text': 'Whatever the longest word in the Harry Potter universe is or the English dictionary is longest word,', 'start': 6563.312, 'duration': 6.746}, {'end': 6574.382, 'text': 'plus 1 should be sufficient to store any name in the story here.', 'start': 6570.058, 'duration': 4.324}, {'end': 6577.425, 'text': 'And then what else does each of these nodes have? Well, it has.', 'start': 6574.703, 'duration': 2.722}, {'end': 6580.326, 'text': 'a pointer to another node.', 'start': 6578.646, 'duration': 1.68}, {'end': 6588.648, 'text': "So here's how we might implement the notion of a node in the context of storing not integers, but names instead like this.", 'start': 6580.647, 'duration': 8.001}, {'end': 6591.849, 'text': 'But how do we decide what the hash table itself is?', 'start': 6589.028, 'duration': 2.821}, {'end': 6598.27, 'text': 'Well, if we now have a definition of a node, we could have a variable in main or even globally called hash table.', 'start': 6591.889, 'duration': 6.381}, {'end': 6599.891, 'text': 'that itself is an array.', 'start': 6598.27, 'duration': 1.621}, {'end': 6607.54, 'text': 'of node star pointers, that is, an array of pointers to nodes, the beginnings of linked lists.', 'start': 6600.974, 'duration': 6.566}, {'end': 6609.422, 'text': 'Number of buckets is kind of up to me.', 'start': 6607.88, 'duration': 1.542}, {'end': 6611.844, 'text': 'I proposed verbally that it be 26.', 'start': 6609.562, 'duration': 2.282}, {'end': 6616.688, 'text': 'But honestly, if you get a lot of collisions, so to speak, a lot of H names trying to go to the same place, well,', 'start': 6611.844, 'duration': 4.844}, {'end': 6621.232, 'text': 'maybe we need to be smarter and not just look at the first letter of their name, but maybe the first and the second.', 'start': 6616.688, 'duration': 4.544}], 'summary': 'Describing a data structure to store names using linked lists and hash tables, with a suggested number of buckets of 26.', 'duration': 82.506, 'max_score': 6538.726, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU6538726.jpg'}], 'start': 6002.157, 'title': 'Data structures and algorithms', 'summary': 'Covers understanding binary search trees, including the impact on search running time with a worst-case scenario of o(n), and discusses hash table data structure, its applications, and hash functions for resolving collisions. additionally, it explains hashing and sorting algorithms, emphasizing practical implications in improving real-world software performance.', 'chapters': [{'end': 6207.773, 'start': 6002.157, 'title': 'Understanding binary search trees', 'summary': 'Explores the concept of binary search trees, highlighting the significance of maintaining balance and the potential impact on the search running time, with a worst-case scenario of o(n) instead of o(log n). it also discusses the potential pitfalls of blindly following the definition and introduces the concept of balanced trees like avl trees and red-black trees.', 'duration': 205.616, 'highlights': ['Binary search trees require maintaining balance to ensure a running time of log n for search operations, as unbalanced trees could devolve to O(n).', 'The design and insertion order of nodes in a binary search tree can significantly impact its balance, potentially leading to a worst-case scenario of O(n) for search operations.', 'Introduction of balanced trees like AVL trees and red-black trees in computer science, which add additional logic to maintain balance and prevent the creation of unbalanced binary search trees.']}, {'end': 6699.566, 'start': 6207.773, 'title': 'Hash table data structure', 'summary': 'Explores the concept of hash table data structure and its applications, discussing the amalgamation of arrays and linked lists to optimize data storage and retrieval, highlighting the use of hash functions to resolve collisions and optimize performance.', 'duration': 491.793, 'highlights': ['The chapter explores the concept of hash table data structure and its applications. The chapter discusses the amalgamation of arrays and linked lists to optimize data storage and retrieval, highlighting the use of hash functions to resolve collisions and optimize performance.', 'The use of hash functions to resolve collisions and optimize performance. The hash function is used to determine the location for input in the hash table, with examples of how names like Albus and Zacharias are mapped to specific locations using a simplistic hash function based on ASCII values.', 'Discussing the amalgamation of arrays and linked lists to optimize data storage and retrieval. The amalgamation of arrays and linked lists in a hash table allows for random access and immediate location jumps while addressing potential collisions that may devolve into linked lists, providing a balanced trade-off for storage and retrieval.']}, {'end': 7034.597, 'start': 6699.586, 'title': 'Hashing and sorting algorithms', 'summary': 'Explains the concept of hashing using a deck of cards and sorting algorithms, illustrating the technique of hashing to resolve collisions and its trade-offs, ultimately discussing the practical implications of hash tables in improving real-world software performance.', 'duration': 335.011, 'highlights': ['Hashing a deck of cards into four distinct buckets takes 52 steps and allows problems of size 13, demonstrating the technique of hashing and its impact on problem size. Hashing a deck of cards into four distinct buckets takes 52 steps, reducing the problem size to 13, showcasing the practical application of hashing.', 'Expanding hashing to include more input, such as the first two letters, results in a significant increase in the number of buckets, demonstrating the trade-offs of hashing for resolving collisions. Expanding hashing to include more input, such as the first two letters, results in a significant increase in the number of buckets, showcasing the trade-offs of hashing for resolving collisions.', 'Despite the theoretical big O notation of a hash table still being O(n) in the worst case, the practical implications of hash tables can result in significant speed improvements over a linked list, emphasizing the tension between theoretical and practical computer science. Despite the theoretical big O notation of a hash table still being O(n) in the worst case, the practical implications of hash tables can result in significant speed improvements over a linked list, highlighting the tension between theoretical and practical computer science.']}], 'duration': 1032.44, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU6002157.jpg', 'highlights': ['Balanced trees like AVL and red-black trees maintain balance in binary search trees to prevent worst-case scenario of O(n) for search operations.', 'Hash functions resolve collisions and optimize performance in hash table data structure, showcasing practical implications in improving real-world software performance.', 'Hashing reduces problem size and demonstrates practical application, showcasing the trade-offs of hashing for resolving collisions.']}, {'end': 7938.645, 'segs': [{'end': 7641.543, 'src': 'embed', 'start': 7616.949, 'weight': 2, 'content': [{'end': 7625.934, 'text': "In the physical world, it's literally something physical like a stack of trays, which have what we would call a LIFO property, last in, first out.", 'start': 7616.949, 'duration': 8.985}, {'end': 7630.037, 'text': "So as these things come out of the washer, they're putting the most recent ones on the top.", 'start': 7626.235, 'duration': 3.802}, {'end': 7635.36, 'text': 'And then you, the human, are probably taking the most recently cleaned one, which means in the extreme,', 'start': 7630.057, 'duration': 5.303}, {'end': 7641.543, 'text': 'no one on campus might ever use that very first Tray, which is probably fine in the world of trays,', 'start': 7635.36, 'duration': 6.183}], 'summary': 'Physical trays have a lifo property, leading to potential lack of use for the first tray.', 'duration': 24.594, 'max_score': 7616.949, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU7616949.jpg'}, {'end': 7723.094, 'src': 'embed', 'start': 7684.532, 'weight': 0, 'content': [{'end': 7687.955, 'text': 'These are here, for instance, as an example of why might you always wear the same color?', 'start': 7684.532, 'duration': 3.423}, {'end': 7693.459, 'text': "Well, if you're storing all of your clothes in a stack, you might not ever get to the different colored clothes at the bottom of the list.", 'start': 7687.975, 'duration': 5.484}, {'end': 7701.425, 'text': 'And in fact, to paint this picture, we have a couple minute video here just to paint this here made by a faculty member elsewhere.', 'start': 7693.539, 'duration': 7.886}, {'end': 7706.91, 'text': "Let's go ahead and dim the lights for just a minute or two here so that we can take a look at Jack learning some facts.", 'start': 7701.445, 'duration': 5.465}, {'end': 7711.591, 'text': 'Once upon a time, there was a guy named Jack.', 'start': 7709.15, 'duration': 2.441}, {'end': 7714.911, 'text': 'When it came to making friends, Jack did not have the knack.', 'start': 7711.991, 'duration': 2.92}, {'end': 7717.972, 'text': 'So Jack went to talk to the most popular guy he knew.', 'start': 7715.432, 'duration': 2.54}, {'end': 7723.094, 'text': 'He went up to Lou and asked, what do I do? Lou saw that his friend was really distressed.', 'start': 7717.992, 'duration': 5.102}], 'summary': 'Example of color choice affecting clothing accessibility, illustrated with a story.', 'duration': 38.562, 'max_score': 7684.532, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU7684532.jpg'}], 'start': 7034.618, 'title': 'Trie data structures and abstract data structures', 'summary': 'Covers trie data structures for achieving constant time lookup, including their multi-tier hash table functionality and space reusability. it also delves into the use of abstract data structures in practical scenarios like printing, tray stacking, email inbox management, and food ordering, addressing associated problems and solutions.', 'chapters': [{'end': 7250.63, 'start': 7034.618, 'title': 'Trie data structure for constant time lookup', 'summary': 'Explains the trie data structure, which allows constant time lookup for massive datasets by creating a tree of arrays, enabling multi-tier hash table-like functionality, and reusing space for names with common prefixes.', 'duration': 216.012, 'highlights': ['The trie data structure allows for constant time lookup, even for massive datasets, by creating a tree of arrays. The trie data structure provides constant time lookup, making it efficient even for large datasets.', 'The trie operates as a multi-tier hash table, storing data based on each letter of the alphabet and enabling efficient storage and retrieval of names. The trie functions as a multi-tier hash table, allowing storage and retrieval of data based on individual letters of the alphabet, providing efficient name storage and retrieval.', "The trie reuses space for names with common prefixes, optimizing storage and memory usage. The trie optimizes storage and memory usage by reusing space for names with common prefixes, such as 'H-A-G' and 'H-A-R', thus reducing redundancy."]}, {'end': 7531.901, 'start': 7251.431, 'title': 'Trie data structure', 'summary': 'Introduces the trie data structure, highlighting its constant time lookup feature and its trade-off of high memory usage for efficiency. it also discusses abstract data structures and the implementation of queues.', 'duration': 280.47, 'highlights': ['The trie data structure allows for constant time lookup, regardless of the number of entries in the data structure, making it particularly compelling compared to other data structures like arrays and linked lists. Constant time lookup, independent of the number of entries in the data structure.', 'Tries consume a significant amount of memory due to the sparsely populated nature of the data structure, making it necessary to make a trade-off between minimizing space and minimizing time. High memory usage due to sparsely populated structure, trade-off between space and time optimization.', "The concept of queues, a common data structure with a 'first in, first out' (FIFO) property, is introduced, and its relevance in computer science and real-world scenarios is explained. Introduction of queues with FIFO property, relevance in computer science and real-world scenarios."]}, {'end': 7938.645, 'start': 7531.921, 'title': 'Abstract data structures in the physical world', 'summary': 'Discusses the use of abstract data structures, such as arrays, linked lists, stacks, and queues, in the physical world, illustrating their relevance in scenarios like printing, tray stacking, email inbox management, and food ordering, while highlighting the potential problems and solutions associated with these structures.', 'duration': 406.724, 'highlights': ["The physical world's use of abstract data structures like arrays, linked lists, stacks, and queues is illustrated in various scenarios, including printing, tray stacking, email inbox management, and food ordering. The discussion highlights the real-world relevance of abstract data structures, such as arrays, linked lists, stacks, and queues, in scenarios like printing, tray stacking, email inbox management, and food ordering.", 'The potential problems and solutions associated with using arrays for printing or storing documents are discussed, emphasizing the risk of running out of memory and the potential solutions like dynamically resizing the array or using a linked list. The potential problems associated with using arrays for printing or storing documents are highlighted, including the risk of running out of memory and the proposed solutions like dynamically resizing the array or using a linked list.', 'The concept of a stack as an abstract data structure is demonstrated in scenarios like tray stacking in dining halls and email inbox management, emphasizing the Last In, First Out (LIFO) property and its implications. The concept of a stack as an abstract data structure is demonstrated in scenarios like tray stacking in dining halls and email inbox management, emphasizing the Last In, First Out (LIFO) property and its implications.', 'The relevance of queues as abstract data structures is exemplified in scenarios like food ordering at a restaurant and the potential problems associated with finite space and storage limitations. The relevance of queues as abstract data structures is exemplified in scenarios like food ordering at a restaurant, highlighting the potential problems associated with finite space and storage limitations.']}], 'duration': 904.027, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/-gpsiMiEOHU/pics/-gpsiMiEOHU7034618.jpg', 'highlights': ['The trie data structure allows for constant time lookup, even for massive datasets, by creating a tree of arrays.', 'The trie operates as a multi-tier hash table, storing data based on each letter of the alphabet and enabling efficient storage and retrieval of names.', 'The trie reuses space for names with common prefixes, optimizing storage and memory usage.', 'Constant time lookup, independent of the number of entries in the data structure.', 'High memory usage due to sparsely populated structure, trade-off between space and time optimization.', 'Introduction of queues with FIFO property, relevance in computer science and real-world scenarios.', 'The discussion highlights the real-world relevance of abstract data structures, such as arrays, linked lists, stacks, and queues, in scenarios like printing, tray stacking, email inbox management, and food ordering.', 'The potential problems associated with using arrays for printing or storing documents are highlighted, including the risk of running out of memory and the proposed solutions like dynamically resizing the array or using a linked list.', 'The concept of a stack as an abstract data structure is demonstrated in scenarios like tray stacking in dining halls and email inbox management, emphasizing the Last In, First Out (LIFO) property and its implications.', 'The relevance of queues as abstract data structures is exemplified in scenarios like food ordering at a restaurant, highlighting the potential problems associated with finite space and storage limitations.']}], 'highlights': ['Python transition simplifies syntax and increases functionality, reducing low-level plumbing and frustration experienced with C.', 'Python allows leveraging more code from libraries and frameworks, accomplishing more with less effort.', 'Copying data for problem-solving can impact running time, especially with large data sets, affecting search and insertion efficiency.', 'realloc function offers efficient array resizing by handling memory movement and freeing old memory.', 'Freeing memory is crucial in dynamic memory allocation to prevent memory leaks, demonstrated using Valgrind.', 'Linked lists optimize memory usage and introduce new syntax for creating custom data structures.', 'Binary search tree offers logarithmic time complexity for searching, improving over linear time complexity of linked lists.', 'Balanced trees like AVL and red-black trees maintain balance in binary search trees to prevent worst-case scenario of O(n) for search operations.', 'Trie data structure allows constant time lookup, reuses space for common prefixes, and operates as a multi-tier hash table.', 'Abstract data structures like stacks and queues have real-world relevance in scenarios like email inbox management and food ordering.']}