### sszcdjr's blog

By sszcdjr, 5 weeks ago,

Hello, Codeforces! & Happy Chinese Teachers' Day!

We (OICon Team) are so excited to invite you to take part in OICon Round 1 (Codeforces Round 896 (Div. 1) and Codeforces Round 896 (Div. 2)) which will start on Sep/10/2023 17:05 (Moscow time). You will be given 6 problems and 2.5 hours to solve them in both divisions.

• Please notice the unusual starting time!
• One of the problems has two versions but their statement are not exactly the same, which means that you can't pass the easy version using the code of the hard version. However, you can only make hacks when you pass both versions.
• There will be $0$ interactive problem in each division so you needn't read the guide for interactive problems.
• Score distribution:
• Div. 1: $500-(500+750)-1000-1750-2500-3000$
• Div. 2: $500-750-1250-(1250+1500)-2500-3250$

The problems were authored and prepared by Error_Yuan, duck_pear, programpiggy and me.

We would like to thank:

Good Luck & Have Fun!

P.S.

UPD1. Editorial is out.

UPD2. Contest is over! Congratulations to the winners!

Div 1:
Div 2:
First Solves in Div 1:
First Solves in Div 2:
• +350

 » 4 weeks ago, # |   +80 As a problemsetter, OICon stands for... SpoilerObviously Incorrect Conclusion :)(idea from our great red sun bilibilitdasc)
•  » » 3 weeks ago, # ^ |   +25 No it should be ...Only Intuitive Conjecture
•  » » » 3 weeks ago, # ^ | ← Rev. 3 →   +89 Actually it should be ...Oh, Incorrect, Comma nder.
•  » » » » 3 weeks ago, # ^ | ← Rev. 3 →   +20 What it actually isOnly Interesting Contests
•  » » » » » 3 weeks ago, # ^ | ← Rev. 3 →   0 I thinkOIers' Convolution
•  » » » » » » 3 weeks ago, # ^ |   0 Oh! I conclude
•  » » 3 weeks ago, # ^ |   0 I thought Olympiad in Informatics Conference
 » 3 weeks ago, # |   +137 Yet another Chinese round!
 » 3 weeks ago, # |   +95 As a tester, I enjoyed the round and found some very nice problems! I recommend you to participate.
•  » » 3 weeks ago, # ^ |   +8 Looking forward to it.
 » 3 weeks ago, # |   +89 As a some-really-interesting-problems-in-this-contest-finder, I tested.Hope all of you can get positive delta!
•  » » 3 weeks ago, # ^ |   0 I just hope everyone gets to learn something and improve their problem solving skills, positive delta would follow!!
 » 3 weeks ago, # | ← Rev. 3 →   +157 As a tester and a member of OICon, I want contribution!This round has many really interesting problems, and I hope all of you can enjoy this round(and get positive delta)!
•  » » 3 weeks ago, # ^ |   +57 Done :)
 » 3 weeks ago, # |   +87 As a first-time tester, I hope you enjoy this round!
 » 3 weeks ago, # |   +73 As another first-time tester, I hope again you enjoy this round!
 » 3 weeks ago, # |   +75 As a rare tester, I don't think it will be very, so called, Chinese, so I do hope you will enjoy this round!
 » 3 weeks ago, # | ← Rev. 2 →   +70 As some strong testers' friend, it seems that this round is fun, but I cannot enjoy it :(Hope u can get positive delta!
 » 3 weeks ago, # |   +72 As a rival of the author, i want negative votes.
•  » » 3 weeks ago, # ^ |   +3 Fun fact: sszcdjr is homosexual:)
•  » » » 3 weeks ago, # ^ |   +17 What is fun about homosexuals?
•  » » » » 3 weeks ago, # ^ |   -32 You are probably the most qualified person here to answer that question
•  » » » 3 weeks ago, # ^ |   +21 Gay round! Whoo!
•  » » » 3 weeks ago, # ^ |   -39 oh he is always looking forward to do gay-ish things on his schoolmates like me :)
 » 3 weeks ago, # |   +59 As a fake author and a fake tester, good luck to you & have fun.Support our team, OICon.
 » 3 weeks ago, # |   +42 "you can't pass the easy version using the code of the hard version"wait what?
•  » » 3 weeks ago, # ^ |   +61 are you cyan at english too?
•  » » » 3 weeks ago, # ^ |   +12 well, English isn't my first language :)
•  » » » » 3 weeks ago, # ^ |   +33 c++ is no one's first language either
•  » » » » » 3 weeks ago, # ^ |   -10 #include int main() { std::cout<<"Say what?"<<"\n"; return 0; } 
•  » » » » » » 3 weeks ago, # ^ |   -30 you know that you can actually say #include int main() { std :: cout << "Say what?\n"; return 0; } 
•  » » » » » » » 3 weeks ago, # ^ |   -19 I was expecting this reply but it was just choice at the moment
•  » » » » » » » » 3 weeks ago, # ^ | ← Rev. 3 →   -25 fair enough. and also maybe you should consider using this line of code: using namespace std; then your code will be much easier to write. for example now the code should be: #include using namespace std; int main() { cout << "Say what?\n"; return 0; } 
•  » » » » » » » » » 3 weeks ago, # ^ |   -13 I do know that... you could see my submissions, thanks tho
•  » » » » » » » » » 3 weeks ago, # ^ |   -16 oh ok, i didn't see your submissions, sorry
•  » » » » » » » » » 3 weeks ago, # ^ |   -13 no worries, it was supposed to be a joke code so I didnt write what I actually do
•  » » » 3 weeks ago, # ^ |   +9 It's obvious that he understood the sentence and was asking 'why the unusuality?'. Perhaps you need to improve your comprehension skills.
•  » » 3 weeks ago, # ^ |   +9 it is said that the easy version is different with the hard version at allInstead of just changing data scale and constraints
 » 3 weeks ago, # |   -25 qp
 » 3 weeks ago, # |   +135 As a ChatGPT, this round is so difficult :(I recommend all the bots to avoid participation, or you'll probably burn your CPUs up.
 » 3 weeks ago, # |   +85 ChatGPT for getting 0 point in both divisions LMAO
•  » » 3 weeks ago, # ^ |   +1 Solving A in 00:00 and 10 unsuccessful hacking attempt ending :P
 » 3 weeks ago, # | ← Rev. 8 →   -8 " There will be 0 interactive problem in each division so you needn't read the guide for interactive problems " Made me Happy.
 » 3 weeks ago, # |   0 Ok lets go!
•  » » 3 weeks ago, # ^ |   0 Meaow!
 » 3 weeks ago, # |   0 Hoping for 1500+ after the contest or at least positive delta. GLHF!
 » 3 weeks ago, # |   +1 orz for no interactive problems. OICon stands for Orz Institute & Constitution
 » 3 weeks ago, # |   +78 Love sszcdjr
•  » » 3 weeks ago, # ^ |   +63 Love sszcdjr
•  » » » 3 weeks ago, # ^ |   +55 Love N_z__
•  » » » » 3 weeks ago, # ^ |   +45 Love shinzanmono
•  » » » 3 weeks ago, # ^ |   +29 Love sszcdjr
•  » » » » 3 weeks ago, # ^ |   +18 Love [DisconnectedGraph]
•  » » » » » 3 weeks ago, # ^ |   0 Love BreakPlus
 » 3 weeks ago, # |   +32 funny emoji :)
 » 3 weeks ago, # |   +26 sszcdjr /se /se /se
 » 3 weeks ago, # | ← Rev. 2 →   +18 Maybe OICon Stands for...[O]nly [I]nteractive [Co]deforces Rou[n]d
•  » » 3 weeks ago, # ^ |   0 But there are no interactive problems,so forget it.
•  » » 3 weeks ago, # ^ |   0 Sdandy for
•  » » » 3 weeks ago, # ^ |   0 Spelling issue
•  » » 3 weeks ago, # ^ |   0 September Fools' Day !
 » 3 weeks ago, # |   +1 Wish i do well and get green
 » 3 weeks ago, # |   +8 Wish getting positive delta and not get back to blue :)
 » 3 weeks ago, # |   +3 Wish getting negative delta and get back to green :)
 » 3 weeks ago, # | ← Rev. 2 →   +52 As a invited-to-but-actually-did-not-test 'tester', wish you positive delta.
 » 3 weeks ago, # |   +2 sszcdjr is great.orz sszcdjr
 » 3 weeks ago, # |   0 I hope my rating will be increased after this contest
 » 3 weeks ago, # |   0 Would it be a round of zero?
 » 3 weeks ago, # |   +3 This is definitely the most interesting contest blog I have ever seen.
 » 3 weeks ago, # |   0 ChatGPT for getting 0 point in both divisions >__<
 » 3 weeks ago, # |   0 What about Pupil Testing ?
 » 3 weeks ago, # | ← Rev. 2 →   +6 No ChatGPT is harmed in this round...(for 0 points)
 » 3 weeks ago, # |   0 Unrelated but does anyone know how long it takes to update the ratings for previous contest problems ?
•  » » 3 weeks ago, # ^ |   0 You're unrated contestant in last div3
•  » » » 3 weeks ago, # ^ |   0 I am asking about problem ratings.
•  » » » » 3 weeks ago, # ^ |   0 oh, my bad. it takes usually 3-5 days.
•  » » » » » 3 weeks ago, # ^ |   0 It usually takes way more time than that.
 » 3 weeks ago, # |   0 Wish me luck
 » 3 weeks ago, # |   0 Orz duck_pear
 » 3 weeks ago, # |   +26 As a Chinese, hope I can get positive delta.
 » 3 weeks ago, # |   0 Wouldn't it be better if it started at 19.35 as usual ?
•  » » 3 weeks ago, # ^ |   0 We authors are in UTC+8, and it will be 22:35 for us if the round starts at the usual time. We want to go to bed earlier :)
•  » » » 3 weeks ago, # ^ |   0 Why you can't start it more ealier like 20:05？
•  » » » » 3 weeks ago, # ^ |   -10 Because one of the authors won't be available before 22:00 (UTC+8) :(
•  » » » » » 3 weeks ago, # ^ |   0 By the way, when you start to prepare for this contest?thx.
•  » » » » » » 3 weeks ago, # ^ |   -10 We proposed the proposal on Feb 2023, and got our coordinator on May.
•  » » » 3 weeks ago, # ^ |   0 But for some other countries wouldn't it be too early
 » 3 weeks ago, # |   +18 Emoji Forces ;)
 » 3 weeks ago, # |   +12 or maybe it's (l)O(l)ICon :))
•  » » 3 weeks ago, # ^ | ← Rev. 2 →   0 or maybe it's (no numerical prize in V)OICon(tét)
 » 3 weeks ago, # | ← Rev. 2 →   +8 The start time is 07:35 PM IST then why is it not started yet?
•  » » 3 weeks ago, # ^ |   +16 I thought the round is today my bad.
 » 3 weeks ago, # |   0 I might be wrong, but I think that the first step to be GM is to put an anime profile photo.
•  » » 3 weeks ago, # ^ |   0 this is same as what i've figured out :lol:
 » 3 weeks ago, # |   0 As sszcdjr's 'ami(e)', j'aime il.
 » 3 weeks ago, # |   +2 The only newbie tester has a performance rating of a master in his only rated contest.A Newbie's reaction: 😱 😱 😱
•  » » 3 weeks ago, # ^ |   0 it means round is too difficult :)
 » 3 weeks ago, # |   0 I hope this is the round where I become specialist(could have become in last div 3 but forgot there was a contest lol!)wish me luck!
 » 3 weeks ago, # |   0 Hoping that unusual time won't become usual again :)
 » 3 weeks ago, # |   -14 My ChatGPT is afraid of getting -154 delta in this round like Mr.Chen (PinkeRabbit) lol
 » 3 weeks ago, # |   +5 In my opinion, OICon=Olympiad in Informatics Conference :P
 » 3 weeks ago, # |   +32 OICon stands for SpoilerOver Implementation Contest
•  » » 3 weeks ago, # ^ |   +5 It happened.222776617
 » 3 weeks ago, # |   0 Hope to become an expert, good luck
 » 3 weeks ago, # |   0 Chinese round from sszcdjr and so on. Sounds loke it will be VERY difficult. Luckily I'm afked. Hope others have fun.
 » 3 weeks ago, # |   0 "you can't pass the easy version using the code of the hard version"wait, what?
 » 3 weeks ago, # |   +5 D1 and D2,,, hope the problem isn't so eccentric
 » 3 weeks ago, # |   +29 Hi, is it only me that m2.codeforces.com is kinda broken? It seems that some of the JS files are replaced with the redirect message. It's not happening in m1 and m3.
•  » » 3 weeks ago, # ^ |   0 For me too.
 » 3 weeks ago, # |   +5 Use of emojis!! cooolll..
 » 3 weeks ago, # |   +3 as a tester hope u enjoy the contest :)
 » 3 weeks ago, # |   0 Yet another Chinese round!OMG interesting dude!
 » 3 weeks ago, # |   -31 Div2 D1&D2 are brilliant!!
•  » » 3 weeks ago, # ^ |   +1 Thought i had D1 in 5 min but after getting 2WA realized i was wrong. Really nice contest!
•  » » 3 weeks ago, # ^ |   0 what's so brilliant about it?
•  » » » 3 weeks ago, # ^ |   -18 I had fun solving them.
•  » » 3 weeks ago, # ^ |   0 what was div 2d?
 » 3 weeks ago, # | ← Rev. 3 →   +1 In the contest when the site went down I submitted the code on m3.Codeforces.com but I had already queued a submission on the main site. The code is exactly the same but I got a 50 points cut because there were two submissions both of which passed. I sincerely hope this issue could be sorted and I could get my actual points in that. Mike and the organisers please look into this.
 » 3 weeks ago, # |   +17 D2 == mystery of pretest 3
 » 3 weeks ago, # | ← Rev. 2 →   +4 WHY in $E$ ($n$ $<$ $10^{18}$) and there is NO pretest where $n$$>$$200$ $??$
 » 3 weeks ago, # |   -8 i love problem B so much
•  » » 3 weeks ago, # ^ |   0 How to solve it?
•  » » » 3 weeks ago, # ^ |   0 Minimum of: distance from a to b distance from a to major city + distance from b to major city
•  » » » » 3 weeks ago, # ^ |   -6 I think it's better written as min(dis(a,b), min(dis(a,majorCity)) + min(dis(majorCity,b))).
 » 3 weeks ago, # |   0 Can someone give any hints about how to solve D1
•  » » 3 weeks ago, # ^ |   -10 For each element you need to give some power of 2 to someone and also take some power of 2 from someone and for each element not equal to the average of the whole array this give take pair is unique. Also if the sum of all elements of the array is not divisible by it's size then answer doesn't exist.
•  » » » 3 weeks ago, # ^ |   0 I was trying to do same thing but got WA on pretest 6. Are there any edge cases ?
•  » » » » 3 weeks ago, # ^ |   0 Idk but i also got WA on pretest 6 due to silly mistake(Writing — instead of +). I also ignored all elements equal to the target final value because we can always use them as the middle man for some operation.
•  » » » » » 3 weeks ago, # ^ |   0 This was my first submission222777285Can you help me figure out the mistake ??
•  » » » » » » 3 weeks ago, # ^ | ← Rev. 2 →   0 idk bro. i didn't do it by manipulating the bits directly but by trying 2 options for each element. Either it gives first some power of 2 and then takes some power of 2 or the other way around and whichever worked without violating the conditions stored it in the map and then checked whether the counts are equal or not222801225
•  » » 3 weeks ago, # ^ |   0 Let S = sum(a), then obviously we need each element to be S/n. For each element find its difference from the target value. Using the constraints (ie everyone must give and get a power of 2), find exactly how much one must give and get (this is the hard part). Then check if each give has a corresponding get.
•  » » 3 weeks ago, # ^ |   0 Each person needs to gain or lose some amount of candles to reach the average. So $a_i - avg = 2^x - 2^y$. It turns out that if $a_i - avg$ is not $0$, then it is either impossible or there is exactly one way to choose $x$ and $y$. Another hint: Since we use powers of two, think about the binary representations.Once you compute $x$ and $y$ for each person, the answer can be found by considering the set of all $x$ and the set of all $y$.
•  » » 3 weeks ago, # ^ |   0 there's at most only a way to make a number that's different from avg equal to avg. Let delta = v[i]-avg. Abs(delta) must be in form "0...01...10..0" and you can just add the first bit before the one part and subtract the last 1 bit (if abs flips the sign you have to flip which bit to add and which to subtract). If delta is 0 you can ignore it, and if it isn't in the case i mentioned, just answer "NO".Now just count all the bits added and subtracted. If this is even for each bit, then answer "YES". (My code 222771034)The idea for D2 was to just consider the case when abs(delta) = "0...010....0". In this case you can just give/get that one bit. I'm not sure why my code fails though
•  » » » 3 weeks ago, # ^ |   0 Ok, editorial says that steps 6-8 aren't needed at all and poor/rich division too.
 » 3 weeks ago, # |   -7 D1 and D2 are amazing problems but i couldn't figure out some edge case apparently ;)
•  » » 3 weeks ago, # ^ |   +3 Div2D once again yeeted my hopes and dreams of becoming CM.
 » 3 weeks ago, # |   -7 How to solve Div2 C?
•  » » 3 weeks ago, # ^ | ← Rev. 2 →   0 I didn't participate and I might be lying like a bitch with this answer but I think it's ans=min(n+1, m) and if m=1 then ans=0. Think about how you can create a pattern when n+1>=m, and therefore get ans=m. Also if n+1
 » 3 weeks ago, # |   +184 I'm sorry, but my solution to F has a complexity of $O(N^2)$. I hope the systest is as weak as pretest.
•  » » 3 weeks ago, # ^ |   +3 Your solution is the fastest :) Do you have a test with TLE?
•  » » » 3 weeks ago, # ^ |   +41 I uphacked my submission with a test like this:$1,-1,1,2,-2,2,3,-3,3,...,n,-n,n$ ($n=166666$)
 » 3 weeks ago, # |   +1 Felt like I was close to getting D2 but just missed. Still might become expert today.
 » 3 weeks ago, # |   0 WA on test 3 div2 B , its time for my mental checkup
•  » » 3 weeks ago, # ^ |   0 i handled k<=1 and max(a,b)<=k case separately maybe try to look into that case tho i'm not sure that it'll affect something in ur code or not.
 » 3 weeks ago, # |   0 Please don't tell me that in Div2 D1 you just have to check if for each element abs(element-avg) should be a power of 2 is the answer. Tell me that this was not it.
•  » » 3 weeks ago, # ^ |   0 This was my first approach which gave WA. So you are good
•  » » 3 weeks ago, # ^ |   +11 this was not it
•  » » 3 weeks ago, # ^ |   0 I checked the balance after breaking the difference of element — avg into two powers of 2(as a swap goes both ways). Any number which is a difference of 2 powers of 2 must have exactly one string of '1s' in its binary representation (we can check using binary subtraction). In other words, 2 ^ (high-bit + 1) — 2 ^ low-bit should be equal to the difference between element and average. Here we are referring to the low-bit and high-bit of the difference. At the end, the balance should be 0 for all bits for a valid arrangement.
 » 3 weeks ago, # |   +28 In div1 , score [2000,2200] is from around 160-th to around 60-th.Many participants are ranked by "the number of dirts" since the total score is quite small. Unfortunately, i'm the one who has many dirts. Sad.
•  » » 3 weeks ago, # ^ |   0 Sorry bro, it's true that the score is quite tight and we should have made the score distribution larger for Div1 :(
 » 3 weeks ago, # |   +19 I wrote $Tlog^3n+mlog^2n$ and got TLE in problem C :(
•  » » 3 weeks ago, # ^ | ← Rev. 2 →   -13 deserve the downvotes ngl
•  » » » 3 weeks ago, # ^ |   +3 I think he is talking about div1 C
•  » » » 3 weeks ago, # ^ |   +3 I mean div.1 C
•  » » » » 3 weeks ago, # ^ |   0 ok mb i didn;t see your rating
•  » » 3 weeks ago, # ^ |   0 I know why I got TLE.I used while ((1 << d) - 1 < n) d++; without longlong so it would loop infinitely.
 » 3 weeks ago, # |   0 Turned out D1 indeed was easy...
 » 3 weeks ago, # |   +7 fixing tons of cases in div1D is frustrating :(
 » 3 weeks ago, # |   -6 My thoughts on the Div2 D1, please help to improve.We can group all people into three types: rich/poor/avg. Rich means he has more than avg candies, and poor means the opposite.We need to record for everyone, how many to give out and how many to receive in.For rich people, suppose he has 111000 (binary) more, then he must receive 1000 (binary) and give 1000000 (binary) since 1000 + 111000 = 1000000;For poor people, suppose he has 110000 (binary) less, then he must receive 1000000 (binary) and give 10000 (binary) since 10000 + 110000 = 1000000;All the above receives and gives must cancel out each other to make the whole party happy.What about the avg people? Well, apparently if they are more than 1, they can just stand in a loop and choose the next one to give and receive from the previous one. What if this is only one avg people? I don't have good thought yet.
•  » » 3 weeks ago, # ^ |   0 The first example shows you what to do with 1 avg person (you can just put them into any chain of transfers as they just pass any received candies straight on).
•  » » » 3 weeks ago, # ^ |   0 Thx!
•  » » 3 weeks ago, # ^ | ← Rev. 2 →   0 avg can just connect two people. instead of a giving to b, a gives to c, which is avg and c gives to bEdit: damn i'm always late for comments today
•  » » » 3 weeks ago, # ^ |   0 Thx!
 » 3 weeks ago, # |   0 Is there a penalty for re-uploading a solution even though if previous one was correct?
•  » » 3 weeks ago, # ^ |   0 According to rules, anything apart from AC and compilation error runs into a penalty. Compilation error I'm not sure but AC won't result in penalty.
•  » » » 3 weeks ago, # ^ |   0 But it did for me,it skipped my 1st upload.
•  » » » » 3 weeks ago, # ^ |   0 If you get a pretests passed and then submit another solution you get the penalty.
•  » » » » 3 weeks ago, # ^ |   0 Apparently only the last solution to pass all test cases is judged. See the contest rules here
 » 3 weeks ago, # |   +69 Terrible difficulty gap, ABC then go to jail
•  » » 3 weeks ago, # ^ |   -16 Sorry, we didn't expect D to be that hard :( Some testers thought it was suitable :(
•  » » » 3 weeks ago, # ^ |   +25 annoying case work
•  » » » » 3 weeks ago, # ^ |   -23 Indeed it can be solved without case working...
•  » » » » » 3 weeks ago, # ^ |   -8 True I think D1 a suitable problem for that range
•  » » » » » 3 weeks ago, # ^ |   -8 Sorry, I thought he was talking about d1 of Div2....I have no idea of D of Div1...pls ignore my previous comment
•  » » » » » 3 weeks ago, # ^ |   +10 How?
 » 3 weeks ago, # | ← Rev. 5 →   +28 (Div2, problem B) I submitted O(N + K) solution written in Kotlin, but I got TL at test 3. Do anyone else have the same situation? Does really result depend on programming language? If so, is it fair enough?UPD: I rewrote my code a bit and got TL 6, where N = max possible value. Honestly, I do not understand the motivation to use such a small time limit in the taskUPD2: My rating decreased -_-
•  » » 3 weeks ago, # ^ |   -21 It is fair, nobody is stopping you from using C++.
•  » » » 3 weeks ago, # ^ |   +7 I agree that it’s fair, but it looks a bit strange for me, especially when I use linear solution and N <= 2 * 10^5 (not really huge number)Anyway, tasks were interesting, I enjoyed the round
•  » » 3 weeks ago, # ^ |   0 Will O(K) pass?
•  » » » 3 weeks ago, # ^ |   0 K <= N, but at least you should input all the positions, so solution is O(N + K) = O(N + N) = O(N)My solution is O(N + K), but I got TL at test 3; then I rewrote my code a bit, but got TL at test 6
 » 3 weeks ago, # |   0 What's with Div 2 D1 pretest 3?
 » 3 weeks ago, # |   0 In div 2 , problem A, problem setter should be ensure us l != r. But he didn't. If l==r , I take range only one index and Xor same index will become ultimately zero If n is odd. I submitted same implement in different approach about six times. But always wrong answer. then I decided to not to take same index instead of using first two index. For a result , number of k also increased. then got AC. But I was always right if l==r according to this problem description. Am I right or not?
•  » » 3 weeks ago, # ^ |   +38 you are wrong. if $l=r$ then $s=a_l$, so you will replace $a_l$ by $a_l$, which does not become $0$. Read the problem statement next time
•  » » 3 weeks ago, # ^ |   0 No bro you are processing the statement of the problem wrong. If the array is [1,2,3] then taking l = 3 and r = 3(1 starting index) you will get XOR as s = 3 so 3 will be replaced by 3. XOR is of all the elements in the range from l to r inclusive. So it will not become 0.
•  » » 3 weeks ago, # ^ |   0 Next time you should use the "Ask a question" tab on the constest front page to clarify it. I also woundered if $l = i = r \implies s = a_i \oplus a_i$, but before guessing that and implementing it, I asked the problemsetters and in a few seconds got the reply "No."
 » 3 weeks ago, # |   -7 A very bad round!!! I'm upset!!!
•  » » 3 weeks ago, # ^ |   +10 I agree, to give so much constructive...
 » 3 weeks ago, # |   0 Problem A edgecase l == r killed me.I need to learn to not make stupid assumptions...
 » 3 weeks ago, # |   +8 What a mathforces round...Div.1A: I just guessed the pattern and proved it by AC.Div.1B: I got to the key observation (Hint 2 in the editorial) relatively fast, but the implementation of B2 took me a long time.Div.1C: I came up with the rest of the solution in ~15 minutes, but I had a hard time dealing with $n \le 10^{18}$. Passed sample tests 1 hour after the contest. (Why is my submission still in queue = =)
 » 3 weeks ago, # |   +1 i do bad at the contest but it has some really good problems like E(of div2) and other problems where really good for them rate
 » 3 weeks ago, # | ← Rev. 2 →   0 Am I the only one who felt Div2 D1 was too much implementation heavy or was it really?
•  » » 3 weeks ago, # ^ |   0 Nah not much of implementation tbh
 » 3 weeks ago, # |   +28 First time hitting 1500))
 » 3 weeks ago, # |   +18 why my and other solutions in queue but another solutions get tests momently
 » 3 weeks ago, # | ← Rev. 2 →   +22 I was close to getting a $\Theta(900 n)$ solution for div2.D1, but kept Wa on Test 3 because I forgot to determine that $2^x - 2^y$ might be unsolvable, and I feel that because I used several unproven conditions, it kept me wondering if the ones I was using were right, thus ignoring the very obvious error of $2^x - 2^ y$.It's a very good problem, but for me, writing about this kind of problem makes it a not that enjoyable experience :(
 » 3 weeks ago, # | ← Rev. 2 →   +15 B1 and B2 are interesting problems, but I solved them for too long time.
 » 3 weeks ago, # |   0 C (Div.2) was a decent one .
 » 3 weeks ago, # |   +40 Congrats to null_awe, finally GM almost half a year after 2399.
•  » » 3 weeks ago, # ^ |   +3 Thanks!（´∀｀）
•  » » 3 weeks ago, # ^ |   0 Meanwhile a clown participated in this just to 2398->2309
 » 3 weeks ago, # |   +30
 » 3 weeks ago, # |   0 Wait I'm assuming that one person can give candies to two or more persons, isn't it? Someone help please.
 » 3 weeks ago, # |   +26 I wrote something wrong in B1,B2 and I only fst B1. Maybe B2 test case too weak? I found a hack of my submission 222782134. But it shows Unexpected verdict in hacks.The test: test1 18 20090905 20090905 20090905 20090905 20090914 20090914 20090908 20090908 20090908 20090908 20090908 20090908 20090908 20090908 20090908 20090908 20090908 20090908
•  » » 3 weeks ago, # ^ |   +8 Sorry, the tests for B2 are a bit too weak. You got the Unexpected verdict because one of the testers' solutions (which is marked with "Accepted") got hacked in your challenge. The test case will be added soon.
 » 3 weeks ago, # |   -29 i want to get minus contribution
 » 3 weeks ago, # |   0 It's a really good contest and let me return to violet, thanks to problems setter~
 » 3 weeks ago, # |   0 ezzzz
 » 3 weeks ago, # |   +10 I posted a video editorial of problem C from Div. 2, I hope you enjoy it and find it interesting.
 » 3 weeks ago, # |   +1 tho it seems that this round isn't that good, but it's still not so bad I think. But ig it's more like guessforces in div.1 A&B1B2.A: I just observed the pattern of the sample. Once you noticed that, it's trivial. Not the best problem in my opinion, but still not bad.B1&B2: I just did it the same as hos.lyric's. Guess the claim mentioned in the editorial, and don't prove it at all. then just pass it.C: Quite educational in my opinion. Though it may be quite standard for some high-rated geniuses?Overall this round isn't that bad. Sure, the problems aren't that nice, but it's not a reason to downvote.
 » 3 weeks ago, # | ← Rev. 3 →   0
 » 3 weeks ago, # |   0 Why is there a popup notification "Can't read or parse problem descriptor" every time I try to open any of problems of these rounds? For example, 1869F - Flower-like Pseudotree won't open.
•  » » 3 weeks ago, # ^ |   0 It looks like it's been a temporary glitch. Now everything is working.
 » 2 weeks ago, # |   0 I usually like chinese rounds. Problems will be observation based.