Fork512Hz's blog

By Fork512Hz, 5 weeks ago, In English

Hello Codeforces!

Solving 5 problems in Educational Codeforces Round 164 (Rated for Div. 2) gave me an unexpected +125 and I leaped across *1800 right into the lower bounds of purple. This means I am finally touching the eligibility to take part in contests with many of the brightest competitive programmers!

Within the 3 months after registering my account, I have learned many new techniques, with the most representative being modular inverse, segment tree with lazy propagation, fenwick tree and Tarjan's algorithm. I really believe segment tree is something like "Welcome to the realms of div.1!" However, my rating revolved around 1790 and was incredibly stable and I doubted if I was improving. But in several training sessions and VPs I managed to do well. Never mind, CM has come, and I finally start to believe I can go on in CP and reach for my goal in an ICPC regional. The next step is to defend CM, and I'm planning to learn:

  • More STL
  • KMP and AC automaton
  • Decomposition and Mo's algorithm
  • Maxflow and Mincut: Dinic's algorithm
  • Euler's sieve
  • Matching on a bipartite?
  • Suffix array of a string?
  • Fast Fourier Transformation?
  • Heuristic searching and pruning techniques?
  • More ad-hoc constructive problems
  • More ad-hoc dp problems

Fun fact: Div 1+2s finish at 1:35AM in China, so I did not register for CodeTON 8 because I would get up early to enjoy cherry blossoms the next day, but when upsolving I solved ABC1C2, skipped D and took down E within 90 minutes and the trip cost me 2 TON...

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5 weeks ago, # |
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Great Work man. Any suggestions for newbie please?

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    5 weeks ago, # ^ |
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    Focus on Greedy and Math Problems, Wish you the best!

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5 weeks ago, # |
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your graph shows really nice progress how did u train ? also how did u handle editorials

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    5 weeks ago, # ^ |
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    chinese do not train, chinese just EXIST

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    5 weeks ago, # ^ |
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    What does "handle editorials" mean? Basically I upsolve problems up to Blue difficulty label(CSP-S+ ~ Provincial selection-) on Luogu. If I stare at the statement for 20mins and have no idea I simply go to the editorial.

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    5 weeks ago, # ^ |
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    Well, what i wonder is how does both of you progress so fast? You are both amazing though.

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      5 weeks ago, # ^ |
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      i guess the same thing i just choose problems way too hard read their editorials and never learn aglos or data structures

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5 weeks ago, # |
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my congratulations!

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5 weeks ago, # |
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Congratulations!

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5 weeks ago, # |
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You must have a very strong mathematical background. It is not possible to reach CM so soon without already being a pro at maths.

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    5 weeks ago, # ^ |
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    Actually I major in Computer science, and some of the required courses include:

    • Data structure
    • Probability and Statistics (I completed this last term so some probability-based problems are easier for me now)
    • Basic discrete math (Sets, graphs, combinatorics)

    I've tried CP in 8th grade as well, and some of the easier techniques are remains from that.

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5 weeks ago, # |
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Congratulations!
Purple is 1900-2199
https://mirror.codeforces.com/blog/entry/20638

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5 weeks ago, # |
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what resources you depend on while learning a new topic ?

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5 weeks ago, # |
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How did you practice? how did you choose your problems? was it randomly? also what advice you would give me so i can reach cyan in the next 2 months

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5 weeks ago, # |
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I believe the choice of some of these algorithms is a bit hasty. I don't think I ever used an FFT, suffix array, Dinic algorithm, Mo algorithm in a Codeforces round, and I left the domain of CM many years ago. Structured understanding of what's out there in C++ STL and what is not is more important, I guess. Dp techniques (again, not very advanced) are also of use.

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    5 weeks ago, # ^ |
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    Thank you for your suggestion. In fact, experienced contestants agree that FFT and suffix array are a bit too advanced for me now, but in the technique-dense Chinese NOI/NOIP, knowing Network Flow and Mo's do make sense. At least for the first 3 topics, their template problems are labeled BLUE difficulty on Luogu.

    Maxflow: P3376 <TEMPLATE> Maxflow

    AC automaton: P3808 AC automaton (Easy version)

    Mo's: P2709 Little B's queries

    Since many problemsetters of XCPC in China have a strong NOI background I believe learning these are of use. But I do agree how to model a problem into a template is the more important part.

    Also: GL World Finals!

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      5 weeks ago, # ^ |
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      Well, I'm only discussing Codeforces specifics. If you're preparing for the Chinese olympiads as well, the priorities should be a bit different.

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5 weeks ago, # |
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Congrats! And I solved 5 problems in that round too and gained +135 rating. It feels great!

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    5 weeks ago, # ^ |
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    how do you pick problems to practice ? do you practice on other judges too?

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5 weeks ago, # |
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Congratss! Any suggestions for Constructive Problems? I have been doing CP for 4 years now (although not regular) but I still have no clue how to tackle them.