cyand1317's blog

By cyand1317, history, 2 years ago, In English,

418 I'm a teapot

Hi everyone! >///<

I'd like to invite you to Codeforces Round #418 which begins at 15:05 MSK on 7 June. Please note that the timing is unusual.

This is my first round here! KAN reviewed the contest and helped me through the preparation process, while Alladdin, neckbosov and Tommyr7 tested all the problems, and MikeMirzayanov and the awesome Codeforces and Polygon platforms made all this happen miraculously. This wouldn't have been possible without your efforts!

The round is rated for the second division, and participants from the first division can take part out of competition. As usual, there are five problems and two hours to solve them. The problems will feature... Well, let's wait and see :)

The scoring distribution will be announced later.

Hope everyone few bugs and fair ratings. Looking forward to seeing you then!

UPD 1 Scoring will be 500-1000-1750-1750-2500. It's recommended to read all problems' statements so as to find the problems that suit you — we tried quite hard to make them clear and interesting.

UPD 2 The round is delayed for 10 minutes due to technical issues. Apologies.

UPD 3 System test is done. Congratulations to the winners!

Div. 2 Top 5

  1. memanon
  2. marmoset
  3. liu_runda
  4. yieldar
  5. krydom

Overall Top 5

  1. xumingkuan
  2. HellKitsune
  3. natsugiri
  4. MakeYanGreatAgain
  5. irkstepanov

Hope you all enjoyed the contest. You all did a great job! The editorial is on the way, please be patient :)

UPD 4 For the impatient, here are the tutorials for problems A to C. More are coming!

UPD 5 The complete editorial is out. Cheers!

 
 
 
 
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2 years ago, # |
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Is it rated?

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Just in case anyone is scratching their head: https://httpstatuses.com/418

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why always scoring distribution is announced later ?

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    2 years ago, # ^ |
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    it's just because you have no girlfriend.

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      2 years ago, # ^ |
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      codeforces is not a place for such shitty jokes.

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          2 years ago, # ^ |
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          purple guys are allowed to say everything

          and blue are not

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            2 years ago, # ^ |
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            I would like to prove you wrong by typing that comment, but I prefer to keep my contribution. It is not purple, but it's because the guy is Bredor. Look through his comments and you will know.

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            2 years ago, # ^ |
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            And don't copy-paste buddy.!Be creative and make your own jokes..!

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          2 years ago, # ^ |
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          Bredor is a famous troll and everyone knows he writes sarcastic comments all the time.

          While your comment was ill-timed and not even funny.

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Hmmm... It seems like Alladdin and amethyst3 are brazzers

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Hope to see a

NORMAL CF ROUND

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    2 years ago, # ^ |
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    What do u mean by "Normal CF round"?

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      2 years ago, # ^ |
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      3000 — A 2000-B 1000-C 500- D 50-E *Numbers of Accepted submissions

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        2 years ago, # ^ |
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        500-D ?? that's normal ?

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    2 years ago, # ^ |
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    You mean you're waiting for the delay ?

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As a tester, wish everyone good luck and have fun!

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Haven't seen a Chinese round for ages. Cool.

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Hope it could be easier than last Chinese Round

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418 I'm a teapot so for this round you will enter as a normal water(current rating )and exit as hot water(current rating+154).

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    2 years ago, # ^ |
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    For what it's worth, I hope you're right.

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      2 years ago, # ^ |
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      It's only for my current rating and to need for make me pupil . But for you it's maybe 129.:D

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        2 years ago, # ^ |
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        Yeah I noticed, but getting 154 wouldn't be bad for me either :D

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          2 years ago, # ^ |
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          I hope you make this done but in my case for getting 154 need more heat that's so hard .

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            2 years ago, # ^ |
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            It is easier to get +154 rating with current 1046 rating, than getting +129 with 1771 rating.

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              2 years ago, # ^ |
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              If God bless me and understand the problem statement !

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              2 years ago, # ^ |
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              int now = Expert(Diversity); // normal water
              int tmp= 154 + 129 + 35(from : rafsan35 );
              int add= tmp/ 6 ;
              now+=add;// Hottttttttt !
              if(now== candidate master(Diversity)){
                  puts("Hellow  candidate master Diversity");
              }
              else{
                puts("Worng ans Bro ! ");
              }
              
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The time when the contest will be started it is 'Iftar Time' (Fast Breaking Time) for Muslim in southern Asia. It will be better and helpful to us if the contest starts an hour later from that time. cyand1317

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    2 years ago, # ^ |
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    Meanwhile it would be quite late for participants from eastern Asia, it's just difficult to meet everyone's needs... :( If the timing does create difficulties, you can try virtual participation later. Apologies for this.

    (It would be great if authors have a list of different regions' occupied time intervals...)

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    2 years ago, # ^ |
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    Suitable for me in Bahrain because it ends an hour before iftar haha

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Auto comment: topic has been updated by cyand1317 (previous revision, new revision, compare).

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    2 years ago, # ^ |
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    It should be 500 — 1000 — 1750 — 1750 — 2500 right?

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      2 years ago, # ^ |
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      Teapots also make mistakes like humans do... You know.

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the time is too unusual

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I am new to this fantastic BLOG where i see many people helping each other out with out any self interest, i am a newbie here and i apologies in advance for any mistakes i might make here ..... http://www.europadtours.com

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Have you noticed that the round number is the reversed contest number ?

Contest number is 814 and the round number is 418.

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Problem C and D have the same score!Amazing!

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    2 years ago, # ^ |
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    They also recommended to read all problems' statements so as to find the problems that suit you

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A 1750 C always makes me upset :(

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Data structures and Constructive algo related problems may be exist in today's round...mathematical term too :)

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10 min extensions seems to be a template.

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Contest extended by 10 mins ... :)

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contest delayed?

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10 minutes fact!!!!!!!!!!!!!!!!!

Coding ended(Ramadan and Iftar fact).

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Everytime :(

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Contest Delayed , Maybe a good time for more contribution .

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It won't be a normal Codeforces round if it is not delayed :D

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Auto comment: topic has been updated by cyand1317 (previous revision, new revision, compare).

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10 minutes delayed???

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A Codeforces contest really cannot be regular without a 10 minute delay, can it :)

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clicked 'ok' to go to contest arena and then 10 minute delay!

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Show the time of the contest 10 minutes later so then u don't have to delay it every time !

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why there's always 10 minutes delay?

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10 mins again

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10 minute delay is a tradition now in Codeforces

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May I ask, what kind of of technical issues causes delay by 10 mins?

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A ten minute delay for me to make a beverage, thank you!

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6000 People registered for the contest. 10 minutes delay means 6000*10 minutes = 1000 hours = 41 days of their life. Just saying. Waiting sucks.. :(

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normal codeforces round = The round is delayed for 10 minutes due to technical issues

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It's about Monogatari! Now it is somewhat interesting. 8-)

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    2 years ago, # ^ |
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    There's some spoilers in task statements lol(but I had already completed mongatari series).

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      2 years ago, # ^ |
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      I am only mid-way through the series, and I am pretty sure I got spoiled by B,C,D — but who cares! I should be fine as long as if I don't lookup for the characters' name in English.

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        2 years ago, # ^ |
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        Actually you don't) Especially B, C and D, they have nothing to do with the plot. While E is taken from the first episodes you would watch.

        I kept that in mind while writing statements so as not to contain spoilers to the anime.

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          2 years ago, # ^ |
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          lol, after reading A and E I assumed that the others are about the actual plot as well.

          Good job for not spoiling the amazing series. :)

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            2 years ago, # ^ |
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            I should have mentioned that in the announcement ._. Did this scare some of you away?

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              2 years ago, # ^ |
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              The oddity within my buggy code did scare some of me away. :P

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                2 years ago, # ^ |
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                Does that part of you want to go home for now? Is Mayoi visible?

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                  2 years ago, # ^ |
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                  The debugger window shows traces of Mayoi within my recusion loop right now.

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Anyone else facing the issue of getting logged out constantly? I had to login at least on five separate occasions during the contest. Not complaining, genuinely want to know whether mine was an isolated case or not.

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this B made me crazy
waiting for the end of contest to see test 6

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    2 years ago, # ^ |
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    also test 2 : In the second sample, 5, 4, 2, 3, 1 is the only permutation to satisfy the constraints.

    dive me crazy , why 4,4,5,3,1 is not accepted !!

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      2 years ago, # ^ |
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      Because {4, 4, 5, 3, 1} is not a permutation of the numbers from 1 to 5.

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        uh, well
        i also misunderstood this point

        thanks

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        i made the permutation but still getting WA on 9.

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        2 years ago, # ^ |
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        can there be more than than 2 positions where ai != bi??

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          2 years ago, # ^ |
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          no , one or two , it can't be more than 2 differrnces

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          No

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            now i got the mistake, i found no. not appearing in a and find the it's correct position. but position was not found correctly in my case.

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      It's a permutation. every integer from 1 to n must appear exactly once

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    2 years ago, # ^ |
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    1.*No number should repeat itself in the list*(I guess testcase 6 stuff!!)
    2.Final list should only differ by 1 from list 'a' and list 'b'
    
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In problem C, n*q should pass but my solution got TLEd on pretest 10. :/ why?

I used sliding window, total operations 2 * 1500 * 200000 = 6 * 108

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    2 years ago, # ^ |
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    Repeating answers are there. Total answers are 26*1500. Store them.

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      2 years ago, # ^ |
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      Yes, there are 26 * n possible answers and you can precalculate them all in O(26 * n^2) using two pointers.

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    Pretest passed for me using the same,maybe it'll fail systest

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    I am afraid that is a bit too slow for a 2s TL, while there exist an O(n^2 * 26) solution.

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      What exactly?

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      why the n^2 ? I think a 2-pointers solution should run in O(n*26)

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        I just preprocessed every single combination that could possibly appear in the query, i.e. for each character O(sigma = 26) and each segment [l, r] O(n*n).

        I don't think you could solve it in O(n*26), even for a sliding window 2-pointer solution it should take O(nq) or O(n*n*26) — but hey! It's surprising to learn that someone solved the question in O(n*26), would you share your method to me?

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          Oh sorry I was mistaken. it's a O(n^2 *26) as well . I forgot the original loop that considers all cases of m.

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    Usually 1 sec is equivalent to 1e8 operations.That's why your solution exceeded the time limit. Btw I implemented an O(N*N*26) solution.

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    My (26 * N2 * log(n)) solution 27641415 got AC which is also around 6 * 108

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    Same here bro :(

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    Hello, using cin.tie() and cout.tie() works fine :)

    My submission

    Even I also got TLE in beginning, but then I just uncommented one line(First line in the main function)

    My first submission with TLE

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What is intended complexity of B solution? I solved it in O(n) and now i'm scared that i've missed something.

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    My complexity is same. P.S. 70 lines of code...

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      Yeah, about 80 for me. Hope it's okay...

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      Mine 61 with a 13-line fast read... Am I missing something?

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    I think it's solvable in O(n) but there's a simple O(n^2) solution: find the two positions in the first array which has the same value(there will be exactly two of them). Replace one of those two positions with each of 1~n and verify if it's valid.

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And how to solve D?

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    Not sure if I will get AC, but I constructed a tree, where x is parent of y if circle y is inside x. Then dp: f[u][x]=maximum area of subtree u if there are x nodes in the first set.

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what is generator command line argument ??

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Is the following solution to D correct? It passed pretests, but I'm not entirely convinced. If circle is inside odd number of circles or 0 circles add its area, else subtract its area.

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    2 years ago, # ^ |
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    i did the same

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    I did DP on graphs

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    2 years ago, # ^ |
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    I think the expected solution is a DP.

    If I understood your algorithm correctly, your algorithm should fail on this case:

    Edit: Incorrect test case

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      Actually the answer here is the area of the large circle + the area of the second largest, which is the same as my algorithm.

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        Ah you were right. I think that solution should AC

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    How do u check how many circles it is inside.

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      You just do O(n^2) to check how many circles contain a particular one.

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        2 years ago, # ^ |
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        No. Like there are 2 circles. How do we check if one if inside the other?

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          2 years ago, # ^ |
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          Distance of two centers is smaller than the difference of two radius

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          2 years ago, # ^ |
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          please help me to understand the below solution has loop as (in main()) for(w=1;w<=9000000000000;w++)  {  r=r+2;  } even then why its not giving TLE? 
          link here
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    2 years ago, # ^ |
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    Yes,its true!If we're taking the outermost circle(not covered by anyone) as a single unit it

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Great round!

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I must be misunderstanding problem C. Can someone explain to me why this solution is wrong?

For each subsequence of s and each character c:

  • moves = count of c in subsequence
  • best[c][moves] = max(best[c][moves], length of subsequence)

Then for each query (m,c) just output best[c][m].

I'm pretty sure my code has no bugs but I keep getting WA on pretest 7.

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    2 years ago, # ^ |
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    I did the same and passed pretests, maybe you are forgetting best[c][moves]=max(best[c][moves],best[c][moves-1])

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      2 years ago, # ^ |
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      Actually I took care of that too, but still WA. :(

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    maybe forget best[c][moves] = max(best[c][moves], best[c][moves — 1]) ?

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    2 years ago, # ^ |
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    best[x][y] can't be greater than n.

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    Haha nevermind, it was a stupid bug where I mixed up the indices of i and c at one point. Good thing this round is unrated for me. :)

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I solved B but i'm interested how did you guys solve it??

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    2 years ago, # ^ |
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    You didn't XD

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    2 years ago, # ^ |
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    Let res be the permutation we need to find. Now it is easy to observe that there can be only at most 2 numbers missing in res according to given a and b arrays. Now find those missing numbers and assign those numbers in missing places in res and check if the res is valid or not.

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2 years ago, # |
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Yeah, it's time to compile error in 20 seconds before the contest ends(27649694).

The reason was that locally I have kotlin 1.1, but cf has only 1.0. Comp error appeared twice in this contest. So sad =(

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2 years ago, # |
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Why remove my point in example test??

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2 years ago, # |
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What is solution of Task C? I think there is pre-calc and DP, but what is rule for dp of this problem?

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2 years ago, # |
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Thank you Chinese for this round :D

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2 years ago, # |
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Very fast System testing!!!

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2 years ago, # |
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I was logged out several times (using google account) which is not nice. Please fix it!

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2 years ago, # |
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What's the intended solution for E? I drafted a O(n^4) (roughly) DP solution for it yet somehow it fails me even on the sample test cases. :/

http://ideone.com/kOBovo

Edit: nvm, I am completely off the track.

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2 years ago, # |
  Vote: I like it +12 Vote: I do not like it

RIP B

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2 years ago, # |
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What is f**cking going with cf? Why I'm loosing task because of compilation error with "M_PI" in GNU C++14, although it's work on my compiler, which is GNU C++14 too?

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    2 years ago, # ^ |
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    Show us the code

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    2 years ago, # ^ |
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    Just googled online and it appears that it has been removed from the C++ standards, RIP.

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      2 years ago, # ^ |
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      Okey, thanx. Now, there is question, why it's still working in compiler in linux?

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      2 years ago, # ^ |
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      Yeah, but GNU C++ should include it. Maybe its because CF runs on windows?

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    2 years ago, # ^ |
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    it's not cf fault :|

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    2 years ago, # ^ |
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    I experienced exactly the same thing when preparing the round. Perhaps you could just add an extra #define... Well, as long as something's learnt you're improving yourself =)

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2 years ago, # |
Rev. 2   Vote: I like it +24 Vote: I do not like it

I can't understand why Reyna solution 27632209 for problem A got WA?!!!

Checker comment Can't find file C:\Contesters\Work\invoker-prod\work\codeforces2\e034999a3f1f1dd18b018c40c84c8c46\check-f7e8e87d48909eaa32eeaee49e520cf4\run\output.fd0138e687.txt.

What is the meaning of that?!!

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    2 years ago, # ^ |
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    Looks like cf error(look at the checker comment).

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    2 years ago, # ^ |
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    500 Internal Server Error :-)

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    2 years ago, # ^ |
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    Something's broken, we will fix that.

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2 years ago, # |
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Auto comment: topic has been updated by cyand1317 (previous revision, new revision, compare).

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2 years ago, # |
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why i got a wrong answer like this?

Can't find file C:\Contesters\Work\invoker-prod\work\codeforces2\838e4a3610786f013367ecfa30b8ac63\check-b58f02c6459228487139e47a79e2e72e\run\output.fd0138e687.txt.

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2 years ago, # |
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What was the approach to solve problem B?

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    2 years ago, # ^ |
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    Just split in two cases, one with only one number who differs, and another with two, use a set in the first case (you need to know the number who is missing) . And in the second case, generate the two possible vectors and use two sets, insert each vector in a different set, and print the one with setsize == n.

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      2 years ago, # ^ |
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      Thanks for your reply, I also read the editorial and your approach is different and also interesting. I think your approach is more efficient, is it O(n)? The editorial approach is O(n^2) I think

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    2 years ago, # ^ |
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    ok, at first, there is a simple observation. a and b can only have at most 2 different positions where the numbers aren't same. So you should think of these 2 cases.

    Case 1 : Only 1 different position(Sample testcase : 3) Here, u should check which is the missing number from 1 to n, and put that into that position

    Case 2 : 2 different position (Sample testcase : 1, 2) Here, there should be 2 missing numbers from 1 to n. try putting them into those positions and see if the permutation is valid. One of them will be valid and that's your answer

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      2 years ago, # ^ |
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      there should be 2 missing numbers from 1 to n
      

      How so? I think even in case 2 there can will be only one number that differs ?

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        2 years ago, # ^ |
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        I think u don't understand what did I mean with missing numbers. ok, look at these.

        4 4 2 3 1
        5 4 5 3 1
        ? 4 ? 3 1
        

        so we know for sure, 1 3 4 is in the permutation and 2, 5 hasn't been used yet. So these are 2 missing numbers which should be used in these two (?) positions

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          2 years ago, # ^ |
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          I think I get the idea. I will read your code submission to understand it :)

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2 years ago, # |
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After seeing the system test, I wish I worked on hacking B. I saw no one was hacking B and thought maybe those pretests were quite good. Alas!

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2 years ago, # |
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Why does greedy approach work in D? In each step of dfs(start from outer circle) try to put new circle to part where it gives positive area. http://codeforces.com/contest/814/submission/27649536

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    2 years ago, # ^ |
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    Well, if we put a new circle (call it "Ci") to part where it gives negative area instead of part where it gives positive area, we lose 2 times of circle Ci's area. No matter how we divide the circles in circle Ci into 2 parts, each part will contribute less than circle Ci's area, so the sum is less than 2 times of circle Ci's area. So it's better to put new circle to part where it gives positive area.

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2 years ago, # |
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What was wrong with test case 22 in B? My output seems to be correct? :/

http://codeforces.com/contest/814/submission/27638764

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    2 years ago, # ^ |
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    your output differs from sequence b in more than 1 position (first and last positions)

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      2 years ago, # ^ |
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      Then Test Case 21 would have given WA as well! Same goes for 18!

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        2 years ago, # ^ |
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        in tc18: your output mismatches sequence a in only one position (third position) and mismatches sequence b in only one position (first position) so it is correct

        in tc21: your output mismatches sequence a in only one position (fourth position) and mismatches sequence b in only one position (first position) so it is correct

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        2 years ago, # ^ |
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        nope. look closely. your output should differ exactly in 1 position. Test case 21, 18 is alright.

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        2 years ago, # ^ |
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        please help me to understand the below solution has loop as (in main()) for(w=1;w<=9000000000000;w++)  {  r=r+2;  } even then why its not giving TLE? 
        link here
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2 years ago, # |
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How my code for Problem C got accepted? I made ans[2000][26] in my code and i was using ans[x][26] in my code. (Due to linear storage of data in cpp? )

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2 years ago, # |
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Can anyone tell why my C fails? Thanks a lot.

Basically for each alphabet I created a vector of <Cost, Profit> where Cost number of color is to be recolored and that would result in a subsegment of that color of at least length Profit. And for each query I just find the upper bound base on m and calculate the answer.

http://codeforces.com/contest/814/submission/27647932

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    2 years ago, # ^ |
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    28 aaaabbbaaabbbbbbbbbbaaaaaaaa 1 3 a

    You'll choose to fill change it into aaaaaaaaaabbbbbbbbbbaaaaaaaa (gives 10) wheareas aaaabbbaaabbbbbbbaaaaaaaaaaa is better (gives 11)

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2 years ago, # |
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Rating update please. I will be expert for the first time :)

It is really very good feeling!

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2 years ago, # |
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Auto comment: topic has been updated by cyand1317 (previous revision, new revision, compare).

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2 years ago, # |
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didn't know CF compiler was so fast that it would support complexity of O(2e5 * 1e3) or O(n * q) for C

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2 years ago, # |
Rev. 3   Vote: I like it 0 Vote: I do not like it
please help me to understand the below solution has loop as (in main()) for(w=1;w<=9000000000000;w++)  {  r=r+2;  } even then why its not giving TLE? 
link here
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2 years ago, # |
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Pretest so weak, FST so much . TnT...

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2 years ago, # |
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Why I got skipped??? I'm sure I didn't copy other people's code.

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2 years ago, # |
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Please note that the ratings are not final now and are going to change a bit because of the issue with a couple of submissions. We will rejudge them and update the ratings, don't worry.

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2 years ago, # |
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Did anyone else assume the garland to be circular. :(

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    2 years ago, # ^ |
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    Yes, it's my carelessness not to mention that it's linear... Though the word "garland" in CF has been used to refer to linear lists quite a few times. Apologies for this. T^T

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2 years ago, # |
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This is the biggest increase of rating ever in codeforces Right ???

This is the biggest increase even after he was hacked on A and B.

(If you can't see the photo click here)

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    2 years ago, # ^ |
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    Well this is weird ... on Mhammad1's profile it shows that his rating change is 803 but on the friend's rating change list it shows that his rating change is 681 ... is this a bug ???

    On the friends rating change list it shows that his rating before the contest was 100 but it actually was -22 ???

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2 years ago, # |
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What is this? I got the same code accepted when I submitted it with GNU 14. But got screwed during the contest as I got TLE with the old GNU 5 version. This is clearly unacceptable.

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2 years ago, # |
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Please Help! Why does testcase 6 fail? Submission

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    2 years ago, # ^ |
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    You are expected to output a permutation of first n number with given condition. Your output have 4 repeated.

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2 years ago, # |
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I solved the D without DP and it worked. code

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    2 years ago, # ^ |
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    Yes, greedy seems to give AC for this. :D Congrats :p

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2 years ago, # |
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For question B, I ran my code in c++14, it gives the wrong answer on test 39 but the same code i tested on c++11 (also on my machine), it gives the correct answer. If is a cf bug? here is my code http://codeforces.com/contest/814/submission/27655109.

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    2 years ago, # ^ |
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    In the function findNum, you check temp[i] != 1 without previously initializing the temp array. So it's up to the compiler to initialize that array with anything (even 1s). The same solution with explicit initialization passes in C++14: 27657207

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2 years ago, # |
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The problems sucked !

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2 years ago, # |
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The first letter of the second word of the problems' name are "aeiou", and prepositions are also different. Interesting name ~ :).

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2 years ago, # |
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Auto comment: topic has been updated by cyand1317 (previous revision, new revision, compare).