Meta Hacker Cup Round 2
Good morning! Meta Hacker Cup Round 2 starts on Saturday, September 24th in under 24 hours! You're automatically registered for Round 2 if you scored at least 15 points in Round 1.
Important info:
- You'll qualify for Round 3 if you place in the top 500 in this round.
- If you place in the top 2000 of this round, you'll win a limited edition Hacker Cup t-shirt.
- If you qualify for Round 3 as well, and you place in the top 200 of round 3, your shirt will have a special "Top 200" badge on it.
We put a lot of effort into these problems, so hope you'll find this contest as almost as balanced Codeforces Global Round 5. Good luck, have fun, and we'll see you on the scoreboard!
Update: Editorial
Finally! I'm sick now but I hope I can get better tomorrow and get a T-shirt! Edit: I couldn't get anything. Maybe next year. Great problems through all the rounds though. I really enjoyed this contest
Very excited for this round!
Just curious, why did you guys decide to host hacker cup rounds in this time period which is different from other competitions like code jam and codeforces rounds?
maybe u just answered your question?
thats insane, but is that rly the reason tho. codejam is in different months and cf rounds probably will change their times for hacker cup
Don't forget to increase stack size. Related link to increase it (c++ & windows)
can you please tell what is the stack size in MB using that number which you mentioned in the video?
I am unable to log in to Facebook due to "required maintenance". Will the contest be postponed?
website is broken (https://www.facebook.com/codingcompetitions/hacker-cup)
Website is working for me, but the log in button is still broken.
Seems to be working for us. Can you try refreshing?
ok it is fixed now for me after resetting cookies and logging back in
Can you check again? Its working for me.
Even in this round, do we get only 5 minutes for submission? Reply fast plz
Yes
Is there any way to see the number of contestants who solve a problem from the scoreboard?
No, not easily yet.
just wanted to suggest something in the Scoreboard UI. Currently, when we fetch the next pages (either using arrow or using start param in queryString), and then we filter out based on country, it displays results from the previously selected offset. It would be better to start displaying results from first page for the selected country because the #pages for a country <= #pages in final scoreboard. I hope that makes sense ?
I am getting "This page isn't available". Am I the only one?
The editorial for A2 says that all numbers are up to 1e9, whereas the problem statement mention that they are up just to 1e6. Which one is correct?
The problem statement.
Please make sure to send t-shirts this year. Didn't receive last years t-shirt. :3
From last year 2700th to this year 935th, I am making progress.
Although I didn't qualify for round 3, it is still satisfactory because I won both Code Jam and Hacker cup T-shirt this year (I didn't get either of them last year). Therefore, no regret.
Just got an AC on D2 10 seconds after the contest :( . Only if there wasn't any validation and all.
One small suggestion if downloading/uploading the tests/results remains in the following years: let people who downloads the full input very close to the final time to still upload the output until the timer is up (i.e. probably a few minutes after the contest ended). It has just happened to me that I downloaded the full input for problem D1 less than one minute before the end of the contest and couldn't upload the solution on time just for a few seconds, and without the overhead of downloading/uploading I would have qualified to the 3rd round :(
Beautiful problems by the way!
Yeah same :(
Bad idea. It basically means extending a contest from 3:00 to 3:05 — assuming that a participant hits "start a timer" early enough.
(One must pass validation first but it can be done with a brute force.)
Yeah, now that you mention it, probably it wouldn't be fair for some people to have a couple of minutes extra. An alternative could be to make validation optional.
I want to fuck everyone who created that system of accepting tasks... Is it so essential to run some testcases locally?
Some laptops have small stack so they got RE when they test their code locally////
From 0 solve last year, I finally qualified for round 3 this year.
But I am not a fan of the Hackercup download and upload format. For D2 it almost took 2 minutes to run my code. I was confused if it was TLE or if the input was too large to process.
Didn't qualify for round 3, but yeah from 0 solved to 2 solved this year, feels good
So, you'd get TL in traditional format
We had a solution that solved it in n*log(n) time. If you had an n*log^2(n) solution, we let that pass as well, though it was a bit more inconvenient for you to run.
Where is my t-shirt for last year's contest?
From what I understand, the hashing function's performance in A2 is based on the assumption that the values in the array would be randomly distributed.
During the round, I also thought that a simple order-agnostic hasher should work, but because any specially designed test case could easily break it, I stopped implementing half-way.
Since no info. was provided in the problem statement on whether the arrays generated would be random or not, is this something 'guarenteed' about hackercup test-cases, that they will always be random unless specified otherwise?
I don't see how the solution assumes that the values are randomly distributed. We can guarantee that the hashes of combinations of numbers are approximately randomly distributed by randomly generating the hash of each integer.
Oh, I'm sorry.
I was grossly overestimating the probability of the sub-arrays differing with 2+ numbers, and was thinking of using the hash function only as a pre-check.
sir it would be great if u can give some good resources to learn more about the topic.Thank you.
Submitted D2 in the last minute and made it to Round 3. Phew...
Spent too much time debugging off-by-one errors.
SecondThread
What's the process of getting the t-shirt? This is first time I have finished amongst top 2000 competitors..
A2 use sigma i, simma i^2, simga i^3%mod , failed on only one testcase.....
Small suggestions, can you make the validate input larger? Seems the validate cases are too little & too small
It would be good to allow users to download all system tests before the contest starts. Anyways, they will be able to open it only when they have the password.
Is there any hacking phase or system testing phase now after this? I wanted to hack my friend's solution
No. You don't deserve friends...
Will there be any plag checks ? I came really close to qualify for round 3 :(
they currently remove cheater users ,my rank also change every minutes .
Yes, there will be/have been
I had a different solution for A2...
i too thought about this idea but i have considered only sum and xor (didn't got idea of product).
i realized that considering only sum and xor doesn't work.
is there any way to prove that there exists same set of elements if sum and xor and product%mod of two different sets are equal ??
I think no. This solution is hackable I guess.
may be ,but i think it is very difficult to find that test case
2, 7, 12 — sum 21 — product 168 — exclusive or 9
3, 4, 14 — sum 21 — product 168 — exclusive or 9
Less than five minutes penalty to reach rank 2000 , I shouldn’t double check my code after passing the validation set next year!
Sadly FSTed in A2 in failed to qualify for Round 3.
My rank became $$${473 \rightarrow 973}$$$ :(
UPD: I just double hashed my single hashed solution and got AC as it was getting WA on just 2 test cases earlier... Hashing is a thing in which we shouldn't trust ;(
I used multiplicative hash trick (similar to XOR hashing).
Which platform did you use to run test cases of A1, my laptop was not able to run the final test cases ;)
Sublime Text with custom input/output.
Don't ever view Input.txt (as sublime text or notepad crashes when we put large amount of input)
Hi. This was my first Hacker Cup. So I don't really know how you operate things. Do I need to contact someone for the T-shirt? Or does someone reach us through email or Facebook?
If you are lucky enough, you will be notified about your T-shirt.
They don't reply to any contacts. You can only sit and wait
I got top 2000 in this round, how do I get the t-shirt? Do I need to contact them?
You will get an email eventually with a link and a code to order
Thanks!
I didn't get that last year
It's that time to get T-shirts again :D
Is there any chance we could get the T-shirts from last year as well? I know many of us didn't receive the T-shirts for 2021, so it would totally make my day to get one, even if it's one year after. (Having the T-shirt is more of a personal-pride thing than anything else; it feels good wearing a T-shirt that I won from a coding contest!)
I read somewhere that they stopped manufacturing 2021 t-shirts, so chances are slim
I ranked 143rd in round 3 last year, where is my T-shirt?
Never got any email from facebook, neither do you reply to my email or DM.
Seeing many comments on the tshirt, I would like to share my experience last year. I almost missed the email on t-shirt because it was sent by a suspicious looking email address and ended up in my spam. I only learnt about it because a kind soul posted something on Codeforces that the weird looking subject title is actually the tshirt email. So I suggest: (i) checking spam folder regularly (ii) any kind soul who received the email to share on Codeforces so that we are all notified.
I also remember it won't be sent so soon — it was sent in Dec last year after the finals.
Actually it will be sent soon; within the next week.
Great, thanks very much!