Thank you for participating in our contest! We hope you enjoyed it.
Please let us know what you thought of the problems by voting!
1952A - Are You a Robot, Again?
Idea: flamestorm
Have you seen the "are you a robot" boxes on websites?
1952A - Are You a Robot, Again?
If you select all the squares with traffic lights and read the corresponding letters from left-to-right, top-to-bottom, you get the text "$$$\texttt{print safety}$$$". So all you need to do is print the word $$$\texttt{safety}$$$.
Idea: willy108
Can you interpret the question in the title another way?
1952B - Is it stated?
You just need to check if there is a substring $$$\texttt{it}$$$ in the string. (That is, the question is asking, "is $$$\texttt{it}$$$ stated?")
Idea: AlperenT
They have fooled? Who have fooled?
The image says April. Could it be about April Fools?
The problem has $$$n \leq 12$$$. Where did you see the number $$$12$$$ before?
1952C - They Have Fooled
Looking at the announcement blog, it can be seen that the first April Fools Day Contest was $$$12$$$ years ago.
The problem asks for the problem count of the April Fools Day Contest that was $$$n$$$ years ago.
The sample that has $$$n = 9$$$ is also given as a hint as there was not an April Fools Day Contest on $$$2015$$$.
1952D - Are You a Procrastinator?
Idea: AlperenT
Are you a procrastinator?
You should be.
What? The checker does not trust you after you say yes? How can you make it believe you?
1952D - Are You a Procrastinator?
The problem asks you if you are procrastinator or not. You should output "yes" (or any other confirmation word that the checker can understand) to solve the problem. However, it does not seem to be enough as the checker responds with "I have no reason to believe you."
You should prove to the checker that you are a procrastinator. You can do this by submitting "yes" in the last $$$15$$$ mins of the contest.
Furthermore, the checker can give different responses depending on your output. Feel free to share what funny responses you got (there are many of them).
Idea: AlperenT
Almost everything in this problem is a hint.
The problem name is "Sweep Line". Does it sound familiar?
Look at the quote in the statement. When does a mistake force you to start all over again?
Why are the numbers in the note section are colored?
Why does the note section contain "I had to take a guess." and "I am literally going to explode."
Minesweeper. This is a slightly different version, since all cells are numbered. Why do the numbers only go up to $$$2$$$?
1952E - Sweep Line
The theme of the problem is Minesweeper.
In Minesweeper, the numbers represent the count of mines around them.
The array given in the input represents a Minesweeper game that is only a line (hence the name Sweep Line). The problem asks you to output the number of possible mine placements that is consistent with the given array.
Note that here each cell refers to the number of mines in the neighboring cells, but not including itself (since the input is only up to $$$2$$$).
The modulo $$$20240401$$$ part is unnecessary as the answer can be at most $$$2$$$ (try to prove this).
Idea: flamestorm
Can you convert a grid of 0s and 1s into a useful piece of data?
Look in the top-left, top-right, and bottom-left corners. What do you notice?
Namely, look at the the top-left, top-right, and bottom-left $$$7 \times 7$$$ subgrids. They form a pattern. Have you seen this pattern elsewhere? (It is well-known.)
1952F - Grid
Replace 0 with white and 1 with black to get this QR code:
Scanning it tells you that you need to find the $$$4 \times 4$$$ grid with the maximum sum.
1952G - Mathematician Takeover
Idea: flamestorm
There is a function that has the same name but different definitions in math and computer science. What is it?
Try to fit a curve through the three points given in the problem. It can help you solve the previous question.
1952G - Mathematician Takeover
The problem is a joke about the function $$$\log$$$. For mathematicians, it means $$$\log_e$$$, but for computer scientists, it means $$$\log_2$$$. In particular, the samples all give the correct output for $$$\log_e(x)$$$, but we really want to output $$$\log_2(x)$$$.
Idea: ToxicPie9
Why are there two examples when each one already has multiple test cases?
A change of perspective might help you solve the problem.
1952H - Palindrome
One obvious weird thing in the statement is that there are 2 sample tests despite the multi-test input format. This implies that the lines ("tests") in each input might not be independent tests and are related in some way.
If we read very closely we might notice two weird things about the statement. First, instead of the usual "Each test case contains a line...", it says "The following t lines each contain...". This is because one line does not correspond to one test case. Another is the unusual definition of palindromes: "in both directions".
This problem is solved by seeing it in a different direction. If we read the third and fourth columns, we may notice that they are palindromes — which read the same in both directions, up and down. The solution is to read $$$t$$$ strings, vertically, from the input and determine whether they are palindromes. Empty strings count as palindromes as you can see in sample 2.
Idea: ToxicPie9
Something looks off with the text (literally).
1952I - Dark Matter
If you stare at the PDF hard enough, you'll notice that some of the text looks curved. Given the hint about "gravitational lensing", it should be clear that this is not a coincidence.
How can gravitational lensing distort text? If there's a lot of mass between you and the text, those matter can bend light going from text into your eyes, making straight text look curved. In addition, the meme image looks normal, implying such mass lies between the image and text (in other words, behind the image from your perspective). Here's a visualization of the configuration:
Now let's do the difficult and technical part: finding the dark matter. To do this we need to first grab some PDF/vector graphics editor like LibreOffice or Inkscape. We can see a lot of random objects behind the image:
These are probably the mass causing distorted text. Unfortunately, as the problem suggests, these objects are dark matter so are transparent because they don't interact with light. We can set their transparency to 0 (or opacity to max) and change their color to see them better:
Which gives the formula $$$(a^2 + b^2) + (a - b) + |a| \times 2b - (ab + 2)$$$. If we plug in $$$a$$$ and $$$b$$$ from the samples, we get $$$1$$$, which corresponds to the missing number in the image. Therefore the solution is to output $$$a + b + ((a^2 + b^2) + (a - b) + |a| \times 2b - (ab + 2))$$$.
1952J - Help, what does it mean to be "Based"
Idea: ToxicPie9
1952J - Help, what does it mean to be "Based"
Update: You can find checker implementations here.
The recent April Fools contests all have problems related to mysterious languages. In this one, you are given several samples in a new, never been seen before constructed language, and your task is to learn it and solve a simple task with it. The idea of using internet slangs as a language was inspired by this meme. The problem format is similar to some Linguistics Olympiad problems.
This problem is rather straightforward: simply figure out what each line of code does, and try to combine known operations to solve the last task. Knowing the meaning of slangs might help in understanding them.
In task 1, we learn 4 operations:
yoink a
: Input an integera
.*slaps a on top of b*
: Adda
tob
.yeet b
: Output the integerb
.go touch some grass
: Return/exit the program.
In task 2 we learn:
bruh b is lowkey just 0
: Assign the variableb
to 0.rip this b fell off by a
: Subtracta
fromb
.
And the less obvious:
vibe check a ratios b
: Check ifa
is larger thanb
. If yes, execute the next line, otherwise don't.simp for 7
: Goto line 7.
In task 3 we learn new things:
yoink a
: Input an entire arraya
.- Indexing operations:
a[0]
. We can also see that arrays are 0-indexed.
These are enough to solve task 4. There are two simple approaches.
- Sort the array and output $$$a[k-1]$$$. We may use bubble sort for easier implementation.
yoink n
yoink a
bruh i is lowkey just n
vibe check i ratios 1
simp for 7
simp for 22
bruh j is lowkey just 1
vibe check i ratios j
simp for 11
simp for 20
bruh k is lowkey just j
*slaps -1 on top of k*
vibe check a[k] ratios a[j]
simp for 18
bruh tmp is lowkey just a[j]
bruh a[j] is lowkey just a[k]
bruh a[k] is lowkey just tmp
*slaps 1 on top of j*
simp for 8
rip this i fell off by 1
simp for 4
yoink k
rip this k fell off by 1
yeet a[k]
go touch some grass
- Since the input integers are distinct, we can loop over each element to see whether exactly $$$k-1$$$ elements are smaller than it.
yoink n
yoink a
yoink k
bruh i is lowkey just 0
bruh m is lowkey just 1
bruh j is lowkey just 0
vibe check n ratios j
simp for 10
simp for 13
vibe check a[j] ratios a[i]
*slaps 1 on top of m*
simp for 19
vibe check m ratios k
simp for 21
vibe check k ratios m
simp for 21
yeet a[i]
go touch some grass
*slaps 1 on top of j*
simp for 7
*slaps 1 on top of i*
simp for 5
Fast editorial
it's prewritten, so it can be fast. and also, it's really goofy so it needs to stay simple enough for people to understand -> fast editorial
buoi dit lon dai chim ia bu dung betele cac lon buoi t se cat cai buoi dit lon dai chim ia bu dung betele cac lon buoi cua m buoi dit lon dai chim ia bu dung betele cac lon buoi dit lon dai chim ia bu dung betele cac lon buoi
oh hey hi there friend
sup
top 10
Thank you codeforces. I procastinated until the end to submit "YES" in D, but you told me I already did submit such a source code.
Thank you codeforces, too. I procastinated until the end to submit "YES" in D, but you told me I already did submit such a source code. (repeat) print("YES")#reeeeepeat
True, in fact, in problem A I wanted to output "NO" then "YES" but gave up the idea after incorrect submission and later on didn't try that for D, LOL
if you have submitted it before the last 15 minutes then you are not a true procrastinators :33
False. I once got the output:
And I was wasting my time with the wrong problem, instead of any other. So I think I still fit the parameters ;)
yeah same problem
Just change the lower/upper casing
well you can just change a bit
Wonderful F!
Was I the only one who created the QR code on pixel art websites ?
nope:)
I used Excel lol
I used Wechat :)
Man problem D was insane. Cannot even cry
are you procrastinating crying as well ?!?!?
:)
i printed "print safety"??
you had to print "safety"
I also did this.
i printed "afety" thinking it says "prints afety" :sob:
I thought I was the only one who did this.
I am not good at English, I consider it as "prints a fety", so I output "fety"
I'm a zoomer I read it as "prints af ety"" so I output "ety"
Based editorial uwu
ce dracu e cacatu asta
What words trigger funny checker responses in D? I managed to get "no", "yes", "lie", "procrastinate", any string containing both "no" and "yes", and the easter egg.
Also, F is nearly impossible without a phone...
no
yes
hello world
heaven
hell
Procrastinator
believe me
i found all of these it is likely that there is more
I tried "believe" and the checker mentioned not lying, does "believe me" do anything more?
'me' is not related sorry
be'lie've just trigger because lie
"?" and "please" too
< gives 'i am too lazy to read that character'
love gives love uwu
I printed "!" (without quote) and got this:
"Your response is too short. I cannot bother replying if you do not respect me enough."
254588860
Any 1 character message gives this response.
ChatGPT
bruh i literally used only websites in laptop for F lmao
"definitely" is recognized as yes
bruh D and J are GOATed fr dude
Great contest, F was a really smart idea.
Problem D T_T I thought i will be the first one to submit xD, but got fooled
I used some insane logics like using sleep to wait 1 second before submitting YES but got absolutely fooled in the end. My entire contest spent on D.
oh damn! haha mine as well plus dark matter
I did G using this solution idea 109323691.
quite interesting idea , similar to this 11823394134
u caught me
good thing about having a slow internet: before the page loads up u see the URL
Thanks for the fun contest! Had a lot of time being trolled (and talking on the "questions about problems" part too) :)
Also whoever came up with the jnybranfnw osnxymbjws rvfqjqrfgp zcaziobjzu rymhtsgare ckkjqfhfrb xfbntvovfq easter egg thing is a genius
saying please also says why are u begging, if u say anything religious: god, devil, heaven, hell, also gives u funny answers
How will we get that QR by just watching the input in F, that is amazing but how can we do that?
just hide the number "1"
I went to paint and started drawing squares on top of one's hoping that one's cut total board in 12 pieces but i noticed qr-code pattern Doing by hands was inconsistent and too long so i searched for online convertor from binary to QR and find this site https://bahamas10.github.io/binary-to-qrcode/
You can fill in the color against the excel sheet and then scan it with your phone. XD
I thought the task was to submit a QR decoder and managed to adapt some QR reader repo (that works on images) to be Codeforces-submittable and work on binary matrices: https://github.com/dpaleka/qr-reader-matrix. Of course, this would WA, because it doesn't produce "12" but "max 4x4 sum", lol.
You can replace 0 with " " and 1 with "█"
That was my idea of using the terminal to do it. Of course the image needs to be resized to a square, but it should work.
I had copied the text into Excel,divide it to a 21x21 square,set all the “1” with black background. I always think that Excel is a best friend with codeforcers
I used turtle module in Python and drew dots of every 1. Then I could easily scan that QR code.
Try Ctrl+F and type
1
.6666
Isn't log normally base 10 in math? and ln is used for base e
Thanks for fast editorial
What does "you have skill issue on speed smh" means in J?
tle?
bro how the hell should someone be able to understand i and e
How to solve E:
broo :skull: :joy:
My dark mode Codeforces extension made all the numbers white :( (though I didn't participate)
Dark Matter really sucks me !!
dude you are sick on the QR thing !
I lost it :DDDD
bfs is fun too
and dijkstra =)
Those who solve these type of questions are the real problem solvers. Literally no meaning. But still how on earth you guys solve it ?
Problem A Totally APRIL FOOLED Me!!!!
cringe problems, cringe authors, i hope the next time the problems will be better
bruh you just lowkey didn't pass the vibe check
that dark matter meme >>>>>>>
I enjoyed solving the C problem, thanks for the contest.
Still did not understand the Line Sweeper with the answer in front of me. Were are the mines supposed to be placed? On a line over the array? On the array?
If the hypothetical placements were a $$$0/1$$$ array $$$b$$$, then the input array $$$a$$$ is just $$$a_i = b_{i-1}+b_{i+1}$$$.
1952F — Grid Can Never think about this... Great question!!
AlperenT is the coolest!
this is what you get if you print AlperenT in D
What does this use to? (If you look at the pdf closely)
That means (almost) the same as megabytes. Kibibyte = 2^10 bytes = 1024 bytes, mebibyte = 2^20 = 1024*1024 bytes = 1024 kibibytes. However, in most cases binary prefixes (kibi, mebi, gibi...) are more correct, because standart SI prefixes, which are commonly used, mean another numbers (kilo- = 10^3, mega- = 10^6, giga = 10^9...)
I also noticed that, moreover, in the Russian version it says 'megabytes', so I thought this mismatch could mean something
I think Code C-- count previous year question from 2012 — 2023
Really become fool, after seeing the editorial of F !!
In D, I printed JNybraNfNW which led me to the easter egg osnxymbjws. Then i printed osnxymbjws which led me to rvfqjqrfgp and asking to give up. Then i printed rvfqjqrfgp which led me to zcaziobjzu and asking me to leave suggesting that all these incorrect submissions causing me Penalty. Then i printed zcaziobjzu which led me to rymhtsgare saying that Fine, this is what you are looking for. Then i printed rymhtsgare which led me to ckkjqfhfrb saying that I have been Fooled. Then i printed ckkjqfhfrb which led me to xfbntvovfq. Finally i printed xfbntvovfq which again sent me to jnybranfnw forming a cycle.
no way someone got fooled like me :OOO i did see the "this will be useful with probability 33/66" thing and totally gave up because of the loop lmao
wtf
How did you even find the first one?
It was commented by willy108 in the Contest's Post's comments.
dang whoever added that easter egg that mustve had a lot of time on their hands and wasted it all
It was so painful to write on assembly without labels.
Will submission be opened, because I would like check my solution to problem J.
Ok, I can submit. What does
wrong answer this ain't it chief... print something
mean?Upd. Ough, I accidentally jumped here to the second line.
106 submissions on C be like: $$$>: ($$$
I even tried to prove I'm a procrastinator by pushing the code to the time limit:(
That code ran for 998ms(just about to TLE), I thought it was procrastnate enough:)
784F - Crunching Numbers Just for You
Same lol.
Same.
Nice Problem I.Hide and Seek
Sad thing was that I used some free online service to remove the (funny! I have recently mentioned it in a conversation) meme from the dark matter pdf, and there wasn't anything visible behind it, so I decided that that wasn't it.
Thank you for the contest though! It was unexpectedly nice
Thanks for this amazing contest. Because of this contest I have finally became specialist, tough luck for people who got negative delta because they weren't able to figure the solutions out.
How dark theme bruh??? Any Extension?
Dark reader
The first contest on CodeForces in which nobody can get AK with 0 penalty theoretically.
problem D was insane.
So, sleep is harmful?
See Number of submissions for 1952C — They Have Fooled of Enchom .... 3rd in today's contest ....
71....
All I knew was there are few inputs and outputs seem small :)
WHAT AN I PROBLEM !!
For question D, assume you do not submit within the last fifteen minutes:
If the string you submit contains affirmative words, such as 'yes', 'sure', you will receive the reply: I have no reason to believe you.
If the string you submit contains negative words, such as 'no', 'never', you will receive the reply: Diagnosis: Skill issue.
If the string you submit contains both affirmative and negative words, you will receive the reply: So you are both a procrastinator and not? I do not believe you.
If the string you submit contains numbers or symbols, you will receive the reply: I am too lazy to learn how to read that character.
If the string you submit contains 'lie', you will receive the reply: I never lie.
If the string you submit is not a keyword, you will receive the reply: I am yet to download enough RAM. Give me short and concise responses that I can understand.
If the string you submit is too short, you will receive the reply: Your response is too short. I cannot bother replying if you do not respect me enough.
If the string you submit is too long, you will receive the reply: Your response is too long. I am too lazy to read all that.
It is important to note that only the first line of the string is checked; other lines of the string are not checked.
This content was derived from an hour of work and dozens of submissions.Crying...
I wanna see J checker
Ah man, problem i was too trivial. I almost had it.
BucketPotato gonna simp you next April Fools contest.
J is the best! I laughed throughout the whole solving process
Question for C
Since "The problem asks for the problem count of the April Fools Day Contest that was n years ago." why in the 1st example for input
0
, so for the current year the answer is10
, if it's 12th contest.Similar for the 2nd example, 1 year ago was 11th contest.
Read this part again but slowly
aah, thanks! For some reason I kept thinking it's about the number of times the competition had been held in history until this year.
deleted
Hey guys, do you know what makes a person drunk after alcohol? A contest whose designer drank alcohol!!! It was wonderful, one of the best contest of my life
the bot roasted me:
it said: wrong answer "no?" diagnosis: skill issue :((
Man, I couldn't solve A because I was only looking for the green lights. Then I tried to take all pictures except for the ones with red lights or where the red arrow on traffic lights points to. Also, I was trying to get the answer counter-clockwise because there was a roundabout sign. After all that, I gave up and gave the picture to Microsoft AI
I submitted 'safety' without even knowing why, just because an AI told me to. So yeah I'm apparently a robot :D
Also, I was sure that the problem name suggests my solution is intentional, and I wondered why so many people had already AC on it.
So, you are more robot than the actual computer? :D
I think the contest should be rated!! Of course, only for legendary grandmasters After seeing our questions, I said: Hey, tourist, where are you? Do you think you can still contest and complete?
Wonderful C
Bruh do the numbers in E actually mean the number of mines in the tiles around it not including itself? I thought it included the tile itself and I got stuck trying to make sense of the samples lmaooo 😂😂🔥🔥 should've realized why the numbers do not exceed 2 instead of 3.
I think I got this thought process because I was trying to solve it as if the grid consists of 2 lines, with the first line being array a and the second line being filled with unopened tiles.
I didn't understand the problem C. Can anyone explain the problem, please?
Thank me later
problem f is so hard to think for me skill issue
"Based"? Are you kidding me? After spending a decent portion of my life procastinating, I finally asked a question and your response to it is "Based"? What do I have to say to you? Absolutely nothing, I am too lazy.", the wise checker said.
Ok so I tryied more the 10 phareses in problem D and I leave the contest 18 minutes before ending
I'm curious about response if one print "No" early. Who tried this, and what feedback did you get?
I assume you mean "Yes". I printed it and got
I know the response of "Yes". I mean exactly "No".
Oh. I printed
Yes No
once (actually, in hindsight, I don't know why I did that but whatever), but never only "No".EDIT: A person above submitted it, you can check what they got.
I tried it. It was -> wrong answer "No"? Diagnosis: Skill issue.
original weed fr
wtf man hahahhah wtf
Mentioning the address of the earth within outer space in the header of problem [I] sounds pretty logical. ONLY aliens can solve it!
Why we can't see the code from other's submissions?
I just noticed, the mine in problem C is written in bold, foreshadowing the minesweeper problem, amazing
Based editorial and vibe check problems ratio editorial.
My screencast
Thank you for fast editorial
The checker in problem D said "wrong answer "let me Ac"? No."
:0
It's my first time to engage april 1st contest, and what hell of F! I spend lots of time on finding the length/area of 12 in the image and was i be fooled?
I can't believe so many submissions for prob F. How to generate the qr with that data
It seems that the codes of other contestants are not yet visible.
If visible, the numbers in the first column should be blue instead of black.
Does anyone else have a similar situation to me? Am I the only one who can't browse other contestants' codes? How to solve this problem? Thanks!
They haven't opened the submissions for viewing yet.
They should be visible to the public now
The checker of J has been published
I submitted after the contest ended LOL (Problem D)
Why didn't anyone solve D for like 1 hour?
Seems simple enough.
A real procrastinator should solve it in last 15 mins, I solved it in last 50 seconds. One of the best procrastinators out there!
I think that if G add the
1 0
testcase then it could have more ACs.Dark matter meme ☠