Hello, friends!
Winter 188th Codeforces Round is coming!
We wished to prepare for you some enjoyable problems (as we believe, not very difficult) with nice ideas and clear statements.
"We" includes authors of the problems yaro and Rei, Codeforces Rounds supervisor Gerald and the platform founder MikeMirzayanov. Special thanks to Pasha (PavelKunyavskiy) and Artem (RAD) for the testing and helpful comments.
Last time I was preparing a competition here on Codeforces, Rounds were still "beta". Well, with less "beta" comes greater responsibility. So I wish the authors and the organizers a successfully held Round. As for the participants, I wish you the unconventional ideas, the clean code (and a clean keyboard, of course), and satisfaction from five (well, possibly the less number will also do...) correct and accepted solutions!
It seems to us that it is not an easy job to arrange the problems by their difficulty, so we have chosen the dynamic scores. Still (out of curiousity) let us put a bet on the following relative difficulties for the problems: div.1 — B-B-C-C-E, div.2 — A-B-C-C-E. How close is our guess?
UPD Sorry for the problems with the Codeforces testing queue during the round.
We will still be happy if you rate our contest (when it will be over): short survey.
And with the gap of one hack the winner of div.1 is meret (Jakub Pachocki)!
Seeing your bet on difficulty levels, Just one question: Are the last 3 questions of div2 not gonna be the same as first 3 questions of div 1..??
Yes, they are.
what is d diff b/w div 1 & div 2? i am a beginner and this is my first contest. what should i opt for- div 1 or 2? plz reply asap
Div 2 for new-comers
it seems like div 2 will be A-B-**D**-**D**-E !!!!
D1 500 = D2 1500, D1 1000 = D2 2000, D1 1500 = D2 2500
This tradition is also a bit strange. The ratios of points are different.
Are you sure that ratios of point must be equals to ratios of difficulties? It isn't clearly.
Exactly!
maybe there will be GAME OF THRONES effect on the problem statement.. :)
'We have to save Robb! He needs your help, but for this you have to find the number of .... to identify the traitor. Please, hurry up!' For example
Since you said for div 2 it's A-B-C-C-E, I guess you meant that it's A-A-C-C-E for div 1?
Or is it A-B-D-D-E for div 2??
C'mon everyone, don't be so peaky :) He only said that the 3th and 4th problem are of similar difficulty.
I hope that this round will be easier because according to the announcement, it seems that this round is going to be difficult. Thanks !
Haaa, Game of Thrones! "Growing Strong" & "As High As Honor"!
contest is prepared by a lot of people thank you all but I hope it will not be like chinese contest
Contest is prepared by 2 person — yaro and Rei. I just wrote extra solutions for more checking.
Thanks yaro and also Rei for the contest!
if it is easy for you, it will also be easy for other people :D
Than the competition becomes a speed competition :D
I participated in two such contests(but it was not simple(AB — very simple and CDE or DE — difficult(solved by 5-30 users)
1) Codeforces Round 163 (Div. 2) (there were 2 very simple problems, third was solved by 80 users, and two last weren't solved) — it's really speed competition
2) Untitled contest
I had a similar experience, where just one unsuccessful hack brought me from position 200 to position 1300 XD
And my schoolmate did one successful hack and comes to position 400 from position 900(but his own solution crashed on final tests)
what is d diff b/w div 1 & div 2? i am a beginner and this is my first contest. what should i opt for- div 1 or 2? plz reply asap.
Div 2
trying opting for div1 !! (only if you could !)
judgement is going very slowly... please check
What the hell is that?! 15 minutes to get a response for the submission?!!!
in queue for more than 10 minutes in Div2 B. judging sucks. :(
still in queue.
very slow judgement, this is becoming very annoying
Queued :(
Yeah, I think is time to upgrade those Pentium II they have, don't you think? In TopCoder this never happens, just saying...
Watch out, people are very sensitive here... My "Queued" comment presses some buttons that the other complaints don't
In topcoder problems there are not super large constraints, so the system test is evaluated quickly... Just saying.
We are talking about the pretests here, which are known for their lack of "super large constraints", whose time-limit is 2s anyway. So, please.
In fact, some pretests can have 'super large constraints' :) I don't know if this contest have it, but well... Have fun and keep coding.
There's no judge results right after the submission. How would it possible to get queue? (Solutions aren't testing on samples)
How is my solution hacked even when i ddnt lock it ??
when you didn't lock your solution it can be hacked but you can resubmit another solution again, but when you lock it, you can't resubmit another solution.
The judegement is very slow. Hope the system test will be finished as soon as possible.
Wow, so many hacks for Div2 Problem C. I guess some coders overlooked the constraints for input data. Anyway, at least it was interesting trying to hack others. Oh and it seems to me that the writers have managed to make a nearly-perfect A-B-C-D-E problem set for DIV2, at least according to number of solvers before sys-test...
For Div2 Problem C.
Maybe some case like this:
-1000000000000000000 1 2
my hacking test for problem C Div 2: -1000000000000000000 1 1000000000000000000
i guess one of reason that the pretest is a bit slow is because many TLE codes for C div 2 :)
thanks yaro and Rei for the contest! :) next time try to make the system testing a bit faster!
how cruel the C in div.2 is! -10^18 1 10^18 is a strong test data.^_^.
Survey for the contest....what a democracy..!
Sad sad sad :-(|) ...
system testing has also been too slow!!! what is the reason?
I guess because of the amount of TLEs in DIV2 C and DIV1 A
All TLEs solutions in A div 1 (C div 2) were hacked, I think. And slow speed of system testing is because slow B div 1 (D div 2) solutions.
Oh,It my best rank until now.
Status of submission 3895303 is still "Running on pretest 8", why?
Because that code is Forrest Gump ..... "Run Forrest Run " ...... :) :
my submission 3887964 for Div-2 B failed on the last test case! :(
oh damn, i forgot to update the volume of vessels...
I don't understand why i was got RTE in div-2 B. I just assign the size of sting s to n and it gets AC. AC link http://codeforces.net/contest/318/submission/3895790 RTE link http://codeforces.net/contest/318/submission/3888165 Can any one explain it?Thanks in advance.
same thing happening to me too...but i got MLE instead of RTE..
RTE: 3887964, AC: 3895821
But i want to know what's the problem with "i<s.size()-4" instead of "i<n-4" where n=s.size().
s.size() returns an UNSIGNED integer, so if s.size() is less than 4
This statement ( s.size() — 4) won't be a negative number! It will be a really big positive number and the loop won't end and it will try to access out of bounds places in the array
You need to cast s.size() to (int), signed int in order to avoid this..
You can print the value of s.size()-4 when s has size less than 4 and see the output yourself.
I had the same problem, and I got the answer.
thank you guys for asking and answering the question.
s.size()
is unsigned, so whens.size() < 4
,s.size() - 4
would be a large unsigned integer, and you'll get RTE.Edit: That's why some people (including me) has a predefined macro
#define SZ(x) (int)x.size()
:DThank's peter50216. Now i have my answer.
Happened with me as well. I should never have ignored those compiler warnings.
the worst thing about codeforces is that the main testing takes place after the contest ,
if it would have told that my solution is wrong after running the test cases during the contest ,i would have corrected my solution this thing needs to be changes,i m not sure even after passing pre test cases whether my solution will increase or not
that's why it's called 'pre'-test
Waiting
Contest rating
update.I think it's A-B-B-D-E for Div 2
And it seems like A-B-E-C-F for Div 1 .^_^.
what do you mean by F ? F...K ?
I mean it's harder than E...it has 3000 point
D (Div. 1) was very similar to TCO 2A Hard. I was able to copy & paste 1/3 of the code.
Is div-2 C can be solved by Extended Euclid?
Div-2 C is simple brute force, but you need to take care of the corner cases where the answer is 0 or -1 or when one of x and y is negative.
It's not a 'simple brute force'. Consider the Test Case -1000000000000000000 1 1000000000000000000. With a pure brute force this TC would definitely give TLE. The trick is to consider the case, when one of the numbers is <0 and the other one >0. And only then you can do brute force. Edit: oh, sorry, I missed the last part of your comment JuanMata
Can any one tell me about SergeiFedorov's solution for Problem E? ... My solution get TLE when Princess && Shadow are within a same block....
Well, I could ))
Idea: if we could reach point outside of the forest, than do it with both points. Then find two nearest trees on the border (one by x coordinate and one by y coordinate) and win :)
If we stand inside the forest and could not get out of it, then just go to the position where shadow stands. Then again to the new shadow position and so on, until we reach it. Of course one should check that they lie in the same component.
I use simple dfs to move from one point to another while inside forest. And greedy one to move to the border trees while points lie outside.
... Wow, this is better ... I have learnd a lesson ... .. Thanks ~~
For all those who solved problem D, where do you get the array?
One way to get it is to precompute it. I left the code I used in my solution: 3891054.
Or precompute it like this: 3896247 (only compute the masks you actually need instead of all; runs 5 secs on my computer).
Interesting round! Can't wait to see editorial for Balance.
link
when is the next round comming?
any hint about Div1 D ?
There is always an option to find our analysis. It's not that hard (I know at least three ways to find it)...