alexwice's blog

By alexwice, history, 11 months ago, In English

Because pre/systests are reasonably good nowadays, hacking is basically a "gotcha" where you screw over people not using custom hash (cpp) or managing their sort (java) or wrapping their integers in a dict (pypy), as this is the main way people get hacked.

For olympiad level contests whether this is good or not is arguable, but when the target audience is those under 1400 rating (Div4), IMO there shouldn't be open hacking. Imagine doing a contest and getting your map<int, int> or dict hacked and therefore receiving a WA on an otherwise acceptable solution, because you didn't know about "splitmix" custom_hash cpp trivia. It just is a hostile experience that IMO shouldn't be in low rated contests. The "ideal" solutions shouldn't involve writing custom hashes for these data structures either imo.

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By alexwice, history, 11 months ago, In English

In recent contests, it seems like we are having readforces, many prompts are many paragraphs long. I think it's okay to have an analogy in the problem statement when it motivates the problem or is useful in explanation. But most problem prompts feel like some 8th grader is just making random references to things they like. A lot of times the analogy is extremely contrived anyways so as to not really be that useful. It makes the problems confusing and harder to understand.

Here are examples from CF885 but this problem happens a lot recently imo.


  • Problem A, why are we running from friends? We should run from enemies. The problem statement isn't even pedagogical.

In an $$$R$$$ by $$$C$$$ grid, you stand at $$$(r_0, c_0)$$$, and $$$K$$$ friends stand at cell $$$(r_i, c_i)$$$ ($$$1 \leq i \leq K$$$). ($$$(r, c)$$$ corresponds to the cell in the $$$r$$$-th row and $$$c$$$-th column.)

Every minute, you must move to a adjacent cell, and then each of your enemies (seeing your choice) must move to an adjacent cell. (Cells are adjacent if they share an edge.)

Can you move in a way to guarantee you never visit any of your enemies forever?


  • Problem D, statement is 5x longer than needs to be:

"You start with a number $$$X$$$ and will perform $$$K$$$ operations. Initially your $$$\text{score}$$$ is $$$0$$$. In one operation you can either add the last digit of $$$X$$$ to $$$X$$$, or add $$$X$$$ to $$$\text{score}$$$. What is the highest score you can achieve?"


Anyways regardless if you agree or disagree (I imagine some will disagree) please leave a comment, I just wanted to start a discussion about this practice. Thanks.

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By alexwice, history, 2 years ago, In English

Construct A Rectangle

A Editorial

Berland Music

B Editorial

Set or Decrease

C Editorial

Shuffle

D Editorial

Math Test

E Editorial

Quadratic Set

F Editorial

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By alexwice, history, 3 years ago, In English
A Editorial
B Editorial
C Editorial
D Editorial
E Editorial
F Editorial
G Editorial
H Editorial

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