Agnimandur's blog

April Fools Day Contest 2022 Editorial
By Agnimandur, history, 3 years ago, In English

All problems were created and prepared by me and magnus.hegdahl. Thanks to BucketPotato, Monogon, and Priyam2k for valuable feedback and testing. Special thanks to MikeMirzayanov for coming up with the idea and preparing the unique checker for 1663H - Cross-Language Program. I hope you enjoyed the contest, and found it to be an interesting series of puzzles.

Example solution code written by Agnimandur is provided for each problem.

1663A - Who Tested?

Clue 1
Clue 2
Solution
Solution Code (Python)

1663B - Mike's Sequence

Clue 1
Clue 2
Clue 3
Solution
Solution Code (Python)

1663C - Pōja Verdon

Clue 1
Clue 2
Solution
Solution Code (Python)

1663D - Is it rated - 3

Clue 1
Clue 2
Solution
Solution Code (Python)

1663E - Are You Safe?

Clue 1
Clue 2
Solution
Bonus Clues (for other problems)
Solution Code (C++)

1663F - In Every Generation...

Clue 1
Clue 2
Clue 3
Solution
Solution Code (Python)

1663G - Six Characters

Clue 1
Clue 2
Clue 3
Solution
Solution Code (Python and Javascript)

1663H - Cross-Language Program

Solution
  • Vote: I like it
  • +92
  • Vote: I do not like it

Comments Comments (46)
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3 years ago, # |
← Rev. 3   Vote: I like it +120 Vote: I do not like it
meme
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3 years ago, # |
  Vote: I like it +20 Vote: I do not like it

I did all possible word searches (normal, normal with diagonal, normal with diagonal with reverse, straight up grid BFS) for "MINOTAUR" and then for both "MINOTAUR" and "THESEUS" but didn't consider doing for just "THESEUS", fml

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    3 years ago, # ^ |
      Vote: I like it +6 Vote: I do not like it

    I did all possible word searches for theseus, got WA. Then I did only the forward-diagonal (i.e. [i0+k][j0+k]) search and got AC. Meanwhile the editorial says you had to do horizontal and vertical searches too. Who's in the right?

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      3 years ago, # ^ |
        Vote: I like it +8 Vote: I do not like it

      Test cases were a bit weak, you had to do horizontal, vertical, and diagonal.

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        3 years ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        IMO it is quite mean, that testcases had backwards-going "theseus" in them but were not considered safe. :D I checked for theseus first (but was also checking theseus backwards ord the other diagonal) but it only passed test 1. Then I checked for minotaur && !theseus as the unsafe condition and got to case 5.

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    3 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    same, smh

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3 years ago, # |
  Vote: I like it +33 Vote: I do not like it

I printed "red panda" for problem A and got accepted???

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    3 years ago, # ^ |
      Vote: I like it +43 Vote: I do not like it

    Ha ha that's an easter egg :)

    Problem A accepts either "bucketpotato" or "red panda" (or various similar combinations).

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3 years ago, # |
  Vote: I like it +4 Vote: I do not like it

Is it normal that i wrote program writing "Red panda" for A?

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

what is meant by "AGC" in problem D?

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3 years ago, # |
  Vote: I like it +39 Vote: I do not like it

is it rated?

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3 years ago, # |
  Vote: I like it +71 Vote: I do not like it

What the actual f-k?

https://codeforces.me/contest/1663/submission/152390392

import random
print("YES" if random.randint(0, 100) % 2 else "NO")

This gets AC in E.

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    3 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    At first I thought that the generator used the same rng, but surely it doesn't work like this, right?

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      3 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Maybe there are like only ~6 tests so it's not too hard for random to pass.

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    3 years ago, # ^ |
      Vote: I like it +56 Vote: I do not like it

    E has 9 tests, so in theory there's a 1/512 chance of this happening lol.

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      3 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Rejudge and see how lucky they really are lmao

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      3 years ago, # ^ |
      ← Rev. 2   Vote: I like it +8 Vote: I do not like it

      Actually, if I recall correctly, CF re-runs your submission two more times in case of getting wrong answer. So the probability of failing all three attempts is $$$\frac{1}{8}$$$, probability of guessing answer in one test case is $$$\frac{7}{8}$$$, while you get AC with $$$\left(\frac{7}{8}\right)^9 \approx 0.3$$$ probability. Really worth a try!

      UPD: It seems that I confused WA and TLE solutions. While it is rather a well-known fact that CF re-runs TLE solutions, it is very strange to do it also with WA ones. Does CF really do it? Is it right to behave so?

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        3 years ago, # ^ |
        ← Rev. 3   Vote: I like it +26 Vote: I do not like it

        CF doesn't seem to do it, because if codeforces actually did it and the chance of bypassing all 9 test with a random solution was 0.3, then with 10 tries i should get AC with 97.8% probability, but i don't. That only can mean that CF make only one attempt on failure or that i'm very unlucky :)

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    3 years ago, # ^ |
      Vote: I like it +28 Vote: I do not like it

    You should try playing poker.

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    3 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    You have chance to pass any problem if you are lucky. Just pring random strings.

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3 years ago, # |
  Vote: I like it +18 Vote: I do not like it

can anyone tell me why I am getting WA in E? I did just like in editorial :(. My submission

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

It is RATED! WTF???

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    3 years ago, # ^ |
      Vote: I like it +4 Vote: I do not like it

    I bet the rating changes will be reverted tomorrow :)

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      3 years ago, # ^ |
        Vote: I like it -10 Vote: I do not like it

      It's obvious, but still very unexpected

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3 years ago, # |
  Vote: I like it +19 Vote: I do not like it

problem G Hard-coding strings solution code isn't available

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3 years ago, # |
  Vote: I like it +3 Vote: I do not like it

I guess the rating changes are only for today .

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3 years ago, # |
  Vote: I like it +34 Vote: I do not like it
Another Solution of H
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3 years ago, # |
  Vote: I like it +15 Vote: I do not like it

Are the rating updates an April Fool's joke?

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Submission Any particular reason why this code for C wasn't accepted?

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3 years ago, # |
  Vote: I like it -8 Vote: I do not like it

Well, it is rated :D

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3 years ago, # |
← Rev. 2   Vote: I like it -33 Vote: I do not like it

I write my user name in A get wrong Why

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    3 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    The answer is either "BucketPotato" or "Red Panda"

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3 years ago, # |
  Vote: I like it +60 Vote: I do not like it

During the contest, after studying Pascal for an hour, I found a clumsy solution for H.

code

I wonder what I was doing :<

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3 years ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

How can I become a expert? It is so hard!!!!!!!!!! T_T

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