Problems that I authored so far

Revision en4, by TheScrasse, 2024-03-21 02:55:23

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 :)

Update after Pinely Round 3

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:

  • I struggled a lot to find a suitable div2A for Codeforces Round 778 (Div. 1 + Div. 2, based on Technocup 2022 Final Round). I proposed a lot of problems that turned out to be unsuitable (for example, because they were too hard), then I used them somewhere else.
  • While I was writing this blog, I realized that 1849E - Max to the Right of Min is identical to my problem preoii_allenamento - Allenamento su ChinaForces, and I could just copypaste the code. Unfortunately I realized this $$$20$$$ minutes after the start of the contest, and I couldn't get the first AC :D
  • Sometimes, if you just remove parts of the statement, the problem becomes better (and sometimes harder)! For example, initially 1854D - Michael and Hotel and preoii_statue - Galleria d'arte were relatively easy problems with a slightly longer statement (e.g., in 1854D - Michael and Hotel it was guaranteed that the input had a special structure), but making the statement simpler also made these problems more interesting.
  • Coming up with a good problem starting from the solution is really hard (at least for me). After failing to generate any difficult problem from the solution, I would say I fully agree with Um_nik's last pro tip.

Authored (roughly sorted by difficulty)

preoii_vm - Aggiornamento della macchina virtuale

Story

cc PATHPAR - Path Parity

Story

cc XORPERM - Xor Permutation

1909A - Distinct Buttons

Story

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

1928B - Equalize

Story

cc SEGFAULT - Segmentation Fault

Story

cc SUBARRAYLEN - Subarrays with length

Story

terry 2023/4 - Viaggio intrigante

Story

1909B - Make Almost Equal With Mod

Story

1909C - Heavy Intervals

Story

cc ANTIKNAPSACK - Anti-knapsack

Story

cc THROWTAKE - Throw and Take

Story

ois_fibonacci - Fibonacci Sequences

Story

1854A2 - Dual (Hard Version)

Story

1909D - Split Plus K

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

1909E - Multiple Lamps

Story

cc NDANDANDOR - Non-decreasing AND and OR

Story

1854C - Expected Destruction

Story

preoii_allenamento - Allenamento su ChinaForces

Story

ois_aliga - A Day in Olbia

Story

cc PERMSEGMENTS - Permutation Segments

Story

1909F2 - Small Permutation Problem (Hard Version)

Story

1854D - Michael and Hotel

Story

1909G - Pumping Lemma

Story

1909I - Short Permutation Problem

Story

1909H - Parallel Swaps Sort

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
Tags author, problemsetting

History

 
 
 
 
Revisions
 
 
  Rev. Lang. By When Δ Comment
en6 English TheScrasse 2024-03-21 03:09:09 343
en5 English TheScrasse 2024-03-21 02:58:07 10 (published)
en4 English TheScrasse 2024-03-21 02:55:23 3550 (saved to drafts)
en3 English TheScrasse 2023-07-30 17:17:11 1 Tiny change: 'e up with [problem:1854C], and I re' -> 'e up with , and I re'
en2 English TheScrasse 2023-07-30 17:15:29 1
en1 English TheScrasse 2023-07-30 17:15:16 16359 Initial revision (published)