Updown's blog

By Updown, 3 months ago, In English,

I recently streamed about persistence, specifically, persistent arrays, persistent segment trees, and persistent union-find. You can check out the stream here.

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By Updown, 3 months ago, In English,

Hi CodeForces!

Last week I streamed about LCA (least common ancestor), Segment trees, and Heavy Light Decomposition. You can check out the stream here. If you already know one or more of those concepts, you can jump to the other concepts.

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By Updown, 4 months ago, In English,

Hi CodeForces,

The week 6/7 stream was about data structures like Fenwick trees and segment trees. Note that you need to know the basic implementation and we go over how to use to solve problems using those.

Here are the problems:

problem 1: CodeForces 961E

problem 2: USACO Balanced Photo

problem 3: USACO Why Did the Cow Cross the Road III

problem 4: USACO Sleepy Cow Sort.

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By Updown, 5 months ago, In English,

Hi CodeForces!

Here is the final dp stream. It is shorter than the other ones (only 1 hour) because we only go over 2 problems.

There were 4 problems for the week but we only go over the 2 hardest ones [prob 3, prob 4].

As a side note, I solved Salesman from IOI 2009 and recorded my thinking/coding/debugging process. You can see that video here. It is a dp + segtree problem.

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By Updown, 5 months ago, In English,

Luqman said he isn't creating a chart of teams going to ACM-ICPC this year as he isn't competing, so I added in all the teams. Let's complete the table together!

For the teams where I don't know the cf handles of the team members, I put their names instead.

Europe

Count Country Region University Member 1 Member 2 Member 3
1 Romania SEERC Alexandru Ioan Cuza University of Iași Juve45 Cristian1997 Sin
2 Switzerland SWERC ETH Zürich TimonKnigge zaspagety Stefanie Zbinden
3 Netherlands NWERC Leiden University pimsp Onno Berrevoets Daan van Gent
4 Ukraine SEERC National Technical University "Kharkiv Polytechnic Institute" vlad8 NegaTeeF Cyber
5 Italy SWERC Scuola Normale Superiore cip999 fram Delfad0r
6 Bulgaria SEERC Sofia University Viktor_Terziev ha1vanka pepi_angelov
7 Germany NWERC Technische Universität München lumibons Gregory fleimgruber
8 Portugal SWERC Universidade do Porto gonP rrp212 Alberto Pacheco
9 Spain SWERC Universitat Politècnica de Catalunya metatron OneStone cescmentation_folch
10 United Kingdom NWERC University of Cambridge aitch Zoli9 lamejeck
11 Serbia SEERC University of Niš — Faculty of Sciences and Mathematics ivan100sic vucislav lazar96
12 United Kingdom NWERC University of Oxford geniucos fanache99 atatomir
13 Estonia NWERC University of Tartu loomas SLLN -is-this-fft-
14 Poland CERC University of Warsaw Radewoosh Chameleon2460 oxytocyna
15 Poland CERC University of Wroclaw yarek Anadi MicGor
16 Croatia CERC University of Zagreb DBradac IvL valkyrie
17 France SWERC École Normale Supérieure de Paris Théophile Wallez Thibaut Pérami Felix Breton

Africa and the Middle East

Count Country University Member 1 Member 2 Member 3
1 Syria Al-Baath University Daniar waow ghostwarrior
2 Syria Aleppo University SmokeOut ThePhenomenal watheq
3 Lebanon American University of Beirut, Faculty of Arts and Science Antoine remyels rayan.94
4 Egypt Cairo University — Faculty of Computers and Information compiler_101 eagle93 wewark
5 Syria Damascus University Nooor I-Love-Islam RamiZk
6 Syria Damascus University Ahmad1 SAeed Mhammad1
7 Egypt Faculty of Computer and Information Sciences, Ain Shams University TripleM5da OreWaFujimiNoKeeDaaa Abdelrhman_Akram
8 Egypt Faculty of Engineering, Cairo University OmarHashim Deathly_Hallows Momentum
9 Egypt Faculty of Engineering- Mansoura University Omar_Elawady abdulla.ashraf sara_elkady
10 Egypt German University in Cairo aabdelzaher Omar_Morsi Kharouba
11 Syria Higher Institute for Applied Sciences and Technology fresher96 Nemane Jessri Anas Kastantin
12 Lebanon Lebanese American University Reckt Ibrahim Heritch karamkontar
13 Syria Syrian Virtual University kingofnumbers RedNextCentury BayHarborButcher
14 Egypt The American University in Cairo johngamal Ramenkami johnsourour
15 South Africa University of Cape Town moyamo Saitama David Broodryk

Asia East

Count Country or Region University Member 1 Member 2 Member 3
1 China Beihang University iwatani ShinriiTin Gengar
2 China Beijing Normal University MisakaKuma Forever_you zhuaiballl
3 China East China Normal University ultmaster kblack zerolin
4 China Fudan University Gromah abc473848880 wxy_z
5 China Guangdong University of Technology Maplesss yang825641085 john123741
6 China Harbin Institute of Technology hsuppr HIT_TOM xpchf
7 North Korea KimChaek University of Technology black_horse2014 kutengine ksi1996
8 China Nanjing University AceSrc gisp_zjz zyb
9 China Nanjing University of Science and Technology Grunt henryrabbit starry2024
10 China Northeastern University (China) Jiujian Chen Baiyu Li Jiaxin Wu
11 China Peking University rxdoi Altria-PenDragon Remilia-Scarlet
12 China Shanghai Jiao Tong University Nisiyama_Suzune mxh1999 sun_en_ze
13 China South China University of Technology yang12138 ying971101 Mappy007
14 China Southeast University, China CoupDeGrace Aguin fifteen
15 Hong Kong The Chinese University of Hong Kong nhho hohomu jasonyik
16 China Tsinghua University JOHNKRAM shigule ufo
17 China Xi'an Jiaotong University zbh2047 I_love_Dayo_Wong Luffbee
18 China Zhejiang University lsmll jiangshibiao lzw4896s
19 China Zhongshan (Sun Yat-sen) University mosfjh africamonkey 8300590

Asia Pacific

Count Country or Region University Member 1 Member 2 Member 3
1 Indonesia Bina Nusantara University hantansu98 AVM.Martin ekeitaro
2 Vietnam Hanoi University of Science and Technology quang ladpro98 _T-T-T_
3 South Korea KAIST ko_osaga alex9801 .o.
4 Japan Kyoto University Go Kato Shunta Masuda Ryoma Sato
5 Taiwan National Chiao Tung University ss1h2a3tw cthbst harryoooooooooo
6 Taiwan National Taiwan University johnchen902 nonamefour0210 wangyenjen
7 Singapore National University of Singapore btzy bayweiheng sidhant
8 South Korea Seoul National University khsoo01 kdh_9949 namnamseo
9 Japan The University of Tokyo sigma425 maroonrk yosupo
10 Indonesia Universitas Indonesia ayaze DigiM IgoRamli
11 Vietnam University of Engineering and Technology — VNU dthangnguyen19 lazyc97 Slumdog
12 Japan University of Tsukuba nuip hugeh0ge reew2n
13 Japan Waseda University ryo_issy imulan DAyamaCTF

Asia West

Count Country University Member 1 Member 2 Member 3
1 Iran Amirkabir University of Technology ParsaA Arpa taxman
2 Bangladesh Bangladesh University of Engineering and Technology _Ash__ Arg_007 t.muttaqueen
3 India Chennai Mathematical Institute rajat1603 AnonymousBunny DP99
4 India IIIT-Delhi Cerberus97 polingy Sullipopa
5 India Indian Institute of Technology — Bombay superman_k pratyush1019 evilbuggy
6 India Indian Institute of Technology — Kanpur yashChandnani Gravito12345 Beast_Within
7 India Indian Institute of Technology — Kharagpur evil666man chestnutrice chenghiz
8 India Indian Institute of Technology — Madras teja349 pranav0123 raja1999
9 India Indian Institute of Technology — Patna equinox i_love_Equinox gear4
10 India Indian Institute of Technology — Roorkee spj_29 deva2802 abhikalpu_123
11 Iran Shahid Beheshti University AminAnvari mrm_196 Erfan.aa
12 Bangladesh Shahjalal University of Science and Technology ovis96 mk_Shahriar Jubair_2147483647
13 Iran Sharif University of Technology M.Mahdi SeyedParsa LiTi

Latin America

Count Country University Member 1 Member 2 Member 3
1 Mexico Escuela Superior De Computo Instituto Politecnico Nacional Marckess galloska alaneos777
2 Mexico ITESM Campus Monterrey eidan EliasMera Diegogrc
3 Brazil Instituto Militar de Engenharia laderlappen samuraiexx rebecacalazans
4 Mexico Instituto Tecnológico Autónomo de México Juanito98 Saat Jacqueline Lira Chávez
5 Mexico Instituto Tecnológico Superior del Sur de Guanajuato sggutier OrlandoIsay Thanya_Leif
6 Brazil Instituto Tecnológico de Aeronautica splucs leaomatheus LucasS
7 Costa Rica Tecnológico de Costa Rica Juan Villacis Luis José Badilla Ortiz Michael Pérez Ocampo
8 Colombia Universidad Nacional de Colombia — Bogotá -osdajigu- mavd09 .vr
9 Argentina Universidad Nacional de Córdoba — FaMAF ec24 mrz MarcosK
10 Peru Universidad Nacional de Ingeniería — FC racsosabe valgt Fischer
11 Argentina Universidad Nacional de Rosario brimix__ mredigonda indexs
12 Argentina Universidad Tecnológica Nacional — Facultad Regional Santa Fe lsantire matramos reaper703
13 Argentina Universidad de Buenos Aires — FCEN teofr aborgna_ aradunsky
14 Cuba Universidad de La Habana blacktools yagamil albexl
15 Cuba Universidad de Oriente — Sede Antonio Maceo ernestico yuriao yordanlp
16 Colombia Universidad de los Andes, Colombia limboguard SparklingRa1n jdanielfandino
17 Brazil Universidade Federal de Campina Grande arthurCF emiso gugabribeiro
18 Brazil Universidade Federal de Pernambuco tfg luucasv diogo
19 Brazil Universidade de São Paulo — Campus de São Carlos samuelfgs LoppA nonsequitur
20 Brazil University of Brasilia Nson Lius rchehab

North America

Count Country University Member 1 Member 2 Member 3
1 USA Carnegie Mellon University bluepichu Yiquan Wang Corwin de Boor
2 USA Colorado School of Mines Samuel Reinehr Joseph McKinsey Matthew Baldin
3 USA Columbia University vlecomte aditya1495 volz.kz.g
4 USA Drexel University Harun duyboy135 Sampriti Panda
5 USA Duke University a142857a Chenwei Wu Xiang Wang
6 USA Harvard University waterfalls Franklyn_W pbt17
7 USA Massachusetts Institute of Technology xyz111 ecnerwala ksun48
8 USA Princeton University roosephu Dingli Yu Xingyuan Sun
9 USA South Dakota School of Mines and Technology lrvideckis mdpfeifer Alexander Iverson
10 USA Stanford University desert97 ericxu0 yum
11 USA The University of Texas at Austin masonsbro mIXs ryanr1230
12 Canada University of British Columbia paulll brandonzhang miseri
13 USA University of Central Florida SecondThread AuroraGarden blockingthesky
14 USA University of Chicago ShakuganSky Zixuan Zhao Yifan Liu
15 USA University of Illinois at Urbana-Champaign BenZ TiChuot97 pittoresque
16 USA University of Nebraska — Lincoln Trieu Hung Tran Khang Phan Dannier Li
17 USA University of Southern California Rating2333 Shizuo anmtcel
18 Canada University of Waterloo --d Xylofo iburinoc
19 USA University of Wisconsin — Madison sengi Assancious divide_by_zero

Northern Eurasia

Count Country University Member 1 Member 2 Member 3
1 Belarus Belarusian State University Lollipop kimden greencis
2 Belarus Belarusian State University of Informatics and Radioelectronics Z38 hloya_ygrt rui-de
3 Georgia International Black Sea University svanidz1 Nika Narushvili Mariam Ksovreli
4 Kazakhstan International IT University Tima LeMans NaughtyMorzh
5 Kazakhstan Kazakh-British Technical University Aeon NurlashKO Zharaskhan
6 Russia Moscow Aviation Institute NikitaMikhaylov ZimakOleg Serhii Horielyshev
7 Russia Moscow Institute of Physics & Technology amethyst0 AndreySergunin irkstepanov
8 Russia Moscow State University LHiC V--o_o--V V--gLaSsH0ldEr593--V
9 Russia National Research University Higher School of Economics qoo2p5 super_azbuka grphil
10 Russia Northern (Arctic) Federal University Svenny ijnhtrgdew Artichoke
11 Russia Saratov State University BledDest Roms adedalic
12 Russia St. Petersburg Campus of Higher School of Economics afedor Eran IgorL
13 Russia St. Petersburg ITMO University PoDuReM josdas romanasa
14 Russia St. Petersburg State University andrey.zavarin AgReB fadeeva.kate.22.03
15 Latvia University of Latvia Pakalns bauldaiselemaitre Ingus
16 Russia Ural Federal University Madball Programmer007 Apollon76

South Pacific

Count Country University Member 1 Member 2 Member 3
1 New Zealand The University of Auckland UoA_ZQC sadobson97 sheepmolester
2 Australia The University of New South Wales DXsmiley SpiritsUnite Adrian Goldwaser
3 Australia The University of Western Australia Theodore Vickery Alexander Thatcher Nicholas O'Callaghan

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By Updown, 5 months ago, In English,

Hi CodeForces!

Last week I made the dp video for my class public as a test, and it seemed really useful so I have decided to make all the videos public.

The second class was also on dp because dp is a very important concept and it shows up very often.

Here were the problems:

Problem 1

Problem 2

Problem 3

Problem 4

Here is the stream with the discussion on how to come up with the solutions. (It starts at about 25 seconds)

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By Updown, 5 months ago, In English,

Hi CodeForces!

I opened registration to my competitive programming course a while ago.

The first class was today on dp and I thought I would make it public as a test to see if it is helpful to make it public afterwards. The video is here. The class starts at 30 mins.

Here were the problems:

Problem 1: Codeforces 910A

Problem 2: Codeforces 22B

Problem 3: USACO Taming the Herd

Problem 4: Codeforces 909C

Note that some of the problems had other solutions, but we discussed the dp solution to problems 1, 2, & 4.

For problem 3, I had already made a video about it and we were running out of time so I skipped it. I made a slightly different video for that problem than I usually make; it was me solving it after seeing it for the first time (basically my thinking process and later my debugging process). I've gotten feedback that this style of videos is better than my other videos, so I'll try to make more videos like this one in the future.

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By Updown, 6 months ago, In English,

Hi CodeForces,

As promised, I am opening registration today for a competitive programming course.

Dates: The classes will go from January 12 to the March 16 (10 classes total). Each class is 1hr 30 mins.

Times: Saturdays 8:30am-10am, 8am — 10am with debugging (PST).

Course:

Based on interest, I am opening course 2.

Course 2: recommended level [1200-1700] most problems: [1300 — 2000] The topics are dynamic programming, depth first search, data structures, binary search, two pointers, implementation and math.

Each class there will be a set of 3-5 problems depending on the difficulty. We will discuss the solution to each problems and the thinking process to arrive at that solution. You can see the my screen, as I am writing on a whiteboard. You can ask questions while the solution is being presented.

There is also an additional debugging section. I noticed that there are people who need help debugging their codes so 30 mins before each class starts (except the first one), I can help you debug your codes from the previous week. The only downside is that the number of people who can sign up for this is limited.

If you are interested, register here! Note that on the previous post, the form was a survey for times. This is the official registration.

I will send out an email to the first few people who register for debugging help letting them know that they got in (and a separate email to those who didn't get in). Unfortunately, if there are too many people, I won't be able to help everyone so I am limiting the sign ups. The first few people who sign up for debugging get in for sure. I am also saving a few spots for those who have been working hard solving problems and can prove it (through things like submissions).

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By Updown, 6 months ago, In English,

Hi CodeForces!

A couple days ago, I posted about some online classes. I got some messages with concerns, so I took the blog down while I figured out a solution. I decided that I will make the classes completely free so that they can help more people.

Dates: The classes will go from the January 5-6 weekend to the March 9-10 weekend (10 classes total). Each class is 1hr 30 mins.

Courses:

I will hold the online course with 10 classes based on the curriculum from my website.

Here are the courses I am thinking of:

Learn C++: (not from my website, includes easy algorithmic problems) recommended level: <700

Course 1: (doesn’t include the learn c++ portion from the website) most problems: [700-1300] recommended level: [700-1000]

Course 2: recommended level [1200-1700] most problems: [1300 — 2000] The topics are dynamic programming, depth first search, data structures, binary search, two pointers, implementation and math

Each class there will be a set of 3-5 problems depending on the difficulty. We will discuss the solution to each problems and the thinking process to arrive at that solution. You can see the instructors screen, so it is as if they are writing on a whiteboard. You can ask questions while the solution is being presented.

There is also an additional debugging section. I noticed that there are people who need help debugging their codes so 30 mins before each class starts (except the first one), I can help you debug your codes from the previous week. The only downside is that the number of people who can sign up for this is limited.

This is open to people from all countries.

If you are interested, fill out this survey about what times and which course you are interested in. Note that the form is not a commitment to signing up for the class, it is just to figure out how many people are interested and at what times.

I will open up registration this weekend once I figure out what time the courses will be held.

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By Updown, history, 7 months ago, In English,

877E - Данил и подработка is an interesting problem that requires queries and updates on subtrees of a tree. It is a great problem to learn a variation of traditional segment trees.

I created a video tutorial explaining the problem. I explained how to order the nodes so that it's possible to use a segment tree and how to do toggle updates.

Here is my YouTube channel with all the video tutorials.

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By Updown, history, 12 months ago, In English,

I created a video solution to the problem 839C. It is a DFS on trees problem.

The tutorial includes a simple code (no defines, etc) that matches the tutorial and a line-by-line explanation of the code while I write it (helpful for those stuck on the implementation of DFS).

Here is the video solution.

Here is my channel with all the video solutions.

As a side note, I am in the process of adding OI problems (such as USACO and APOI) to Course 3 of VPlanet because I realized that there isn't anywhere to find OI problems separated by topic.

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By Updown, 15 months ago, In English,

Problem 698A is a typical dynamic programming problem (without optimizations or other tricks) making it a great problem to learn dynamic programming from.

I created a video tutorial for those who are struggling with dynamic programming. I realize that a lot of people already know dynamic programming but there are also many people who this tutorial could benefit.

I hope this is useful and let me know what you think!

Here is the channel with all the videos.

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By Updown, history, 18 months ago, In English,

Last week I posted about a new website I'm starting: http://vplanetcoding.com.

I added a dynamic programming video tutorial for 855B - Marvolo Gaunt's Ring. I explained the idea behind dynamic programming and how to use dynamic programming to solve the problem.

Here is the solution. I sped up the end a little bit to keep the video short.

Unlike the DFS video I made, I didn't feel the need to explain my code because I explained it as I solved the problem. I did, however, make sure I used the same variables, loops and formulas in the code as I used while explaining the solution to the problem.

In addition, I am in the process of adding a bunch of Codeforces and USACO problems sorted by topic and difficulty to the website. I have added several problems and topics at every level. These topics include tree traversal, DP on trees, binary search, and loops. These topics have a problem but I haven't added video tutorials yet.

Here is my YouTube channel with the video tutorials.

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By Updown, history, 18 months ago, In English,

I noticed that there aren't too many video tutorials for Codeforces problems. There are text editorials but the solutions can be hard to understand and/or implement. Because of this, I decided to create a website with video tutorials of Codeforces & USACO problems. I'm also dividing the problems by topic and difficulty.

The website is a work in progress. Here is the website: https://www.vplanetcoding.com/.

I started this website by taking one problem, 893C - Rumor, and creating a video tutorial explaining Depth-First Search(DFS) and connected components while solving the problem. At the end of the video, I wrote the C++ code without complex syntax and I explained the code, line-by-line, as I wrote it.

I think that explaining the code for the solution will help a lot of people implement the solution.

I know that many people know DFS and connected components, but there are many people who don't know DFS and connected components who this tutorial will benefit.

Here is the video: https://www.vplanetcoding.com/course-2-standard-algorithms-and-data-structures#1.

Let me know if you have feedback. Also, let me know which problems I should create video tutorials for next.

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