TheScrasse's blog

By TheScrasse, history, 7 months ago, In English

Hi everyone,

after Codeforces Round 889 (Div. 1), maybe it's time to collect all my problems here. For now, I've mainly invented easy-ish problems. I wish to invent a very hard problem sooner or later :)

I'm putting the story of each problem under spoiler, because it may contain parts of the solution. I invented many problems by just trying random setups until I came up with something solvable, but some problems (especially the harder ones, for example 1854D - Michael and Hotel) may have more interesting stories.

Fun facts:

Authored (roughly sorted by difficulty)

preoii_vm - Aggiornamento della macchina virtuale

Story

cc PATHPAR - Path Parity

Story

cc XORPERM - Xor Permutation

1485A - Add and Divide

Story

cc SUMPRODSEG - Sum Product Segments

Story

cc MXMODSUM - Maximum Pairwise Modular Sum

Story

1855B - Longest Divisors Interval

Story

terry 2023/3 - Dipingere i muri

Story

1485B - Replace and Keep Sorted

Story

cc SEGFAULT - Segmentation Fault

Story

cc SUBARRAYLEN - Subarrays with length

Story

terry 2023/4 - Viaggio intrigante

Story

cc ANTIKNAPSACK - Anti-knapsack

Story

cc THROWTAKE - Throw and Take

Story

1854A2 - Dual (Hard Version)

Story

1485D - Multiples and Power Differences

Story

1854B - Earn or Unlock

Story

preoii_armadio - Evasione dall'armadio

Story

UOI 2023/7 - Add Again

Story

1485E - Move and Swap

Story

1485F - Copy or Prefix Sum

Story

cc NDANDANDOR - Non-decreasing AND and OR

Story

1854C - Expected Destruction

Story

preoii_allenamento - Allenamento su ChinaForces

Story

cc PERMSEGMENTS - Permutation Segments

Story

1854D - Michael and Hotel

Story

Partially authored (roughly sorted by difficulty)

1654A - Maximum Cake Tastiness

Story

preoii_triplets - Comune di Alleib

Story

1485C - Floor and Mod

Story

arc147_c - Min Diff Sum

Story

preoii_permutazione2 - Trova la permutazione

Story

preoii_sets - Insiemi nell'armadio

Story

1762E - Tree Sum

Story

preoii_statue - Galleria d'arte

Story

UOI 2023/4 - Array and prefix sums

Story

1654H - Three Minimums

Story
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7 months ago, # |
  Vote: I like it +1 Vote: I do not like it

I love your questions because of how concise they are.

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7 months ago, # |
  Vote: I like it +1 Vote: I do not like it

I wish people like you become immortal and stay healthy.

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7 months ago, # |
  Vote: I like it +10 Vote: I do not like it

Thanks! I like the problem 1854C & 1854D.

by the way what is the random solution from JOI 2019 — Virus Experiment ?

  • »
    »
    7 months ago, # ^ |
    Rev. 2   Vote: I like it +18 Vote: I do not like it

    I guess this is an implementation of the random solution.

    The main idea is that you simulate the process starting from random nodes, and you can discard some nodes (i.e., they don't achieve the minimum number of infections) if you end up in a past starting point. The complexity is $$$O(n \log n)$$$ on average. The initial version of my problem was basically this idea, made interactive.