tourist's blog

Codeforces Round #127
By tourist, 12 years ago, translation, In English

Hello everyone!

As many of you already know, today is the day for Codeforces Round #127 missing which is really undesirable ;)

Original problems for you were created by tourist and Romka. We tried to emphasize the ideological component of the problems, thus we hope that you'll spend more time thinking than coding. Special thanks for helping in setting the contest go to Codeforces coordinator Gerald. We also thank Delinur for translating the problem statements and Alex_KPR for reviewing them.

We hope that this round won't be just a regular Codeforces round for you, but will bring you new experience and new knowledge. For the authors all problems are equally easy, yet we tried to arrange them in decreasing order of simplicity :)

Problems' point values in Division 1 are 1000-1000-1500-2000-2500. Problems' point values in Division 2 are 500-1000-2000-2000-2500.

Wish you success!

UPD: The contest is over, thanks all for participating. We hope you enjoyed it :)

In Division 1 rng_58 was a clear winner, solving all 5 problems in an hour and a half! No one else managed to solve all problems in two hours.

The winners in Division 1 are (full results):

  1. rng_58

  2. peter50216

  3. liympanda

  4. White_Bear

  5. havaliza

In Division 2 every problem was solved by somebody, but nobody managed to solve all problems. The battle was very tough and the gaps were very small.

The winners in Division 2 are (full results):

  1. Leewings

  2. snow_lotus

  3. 72VanVector_SevNTU

Congratulations to the winners!

UPD2: The editorial is available now.

  • Vote: I like it
  • +305
  • Vote: I do not like it

Comments Comments (57)
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12 years ago, # |
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This will be my 1st participation ever on a codeforces round!! I am looking forward to it

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12 years ago, # |
  Vote: I like it +6 Vote: I do not like it

As points seem to be in increasing order, it suggests that also the difficulty of tasks is increasing rather than decreasing... am I right? :)

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    12 years ago, # ^ |
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    Yes, you're right: in Russian version it's written: "in decreasing order of simplicity".

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      12 years ago, # ^ |
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      Thanks man, always good to know where to start :)

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    12 years ago, # ^ |
      Vote: I like it +24 Vote: I do not like it

    Yes, I meant "in decreasing order of simplicity" :) Thanks, I've corrected it.

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12 years ago, # |
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"yet we tried to arrange them in decreasing order of difficulty :)"

decreasing order with points increasing?

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    12 years ago, # ^ |
      Vote: I like it +11 Vote: I do not like it

    That was a mistake, sorry. It should be "in decreasing order of simplicity", of course.

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12 years ago, # |
  Vote: I like it +20 Vote: I do not like it

"...we hope that you’ll spend more time thinking than coding..."

I really like the idea ;-)

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12 years ago, # |
← Rev. 2   Vote: I like it +11 Vote: I do not like it

"For the authors all problems are equally easy, yet we tried to arrange them in decreasing order of simplicity :)" Nevertheless, we recommend you to read all the statements and hope you won't get stuck on one problem losing possibility to solve other problems.

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12 years ago, # |
  Vote: I like it +4 Vote: I do not like it

I Hope Short statements ,easy to understand and more thinking.

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12 years ago, # |
  Vote: I like it +9 Vote: I do not like it

I feel it will be hot !!!

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12 years ago, # |
  Vote: I like it +56 Vote: I do not like it

I was the author of this problem... http://community.topcoder.com/stat?c=problem_statement&pm=11133

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    12 years ago, # ^ |
    ← Rev. 2   Vote: I like it +16 Vote: I do not like it

    So Ivan won't accept that problem for Torcoder? :)

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      12 years ago, # ^ |
        Vote: I like it +26 Vote: I do not like it

      I don't think the SRM's problem contains a permutation of the codeforces's problem as a subsequence :)

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    12 years ago, # ^ |
      Vote: I like it +15 Vote: I do not like it

    Turns out it wasn't a brand new problem [:|||:] :)

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    12 years ago, # ^ |
      Vote: I like it +19 Vote: I do not like it

    We're really sorry that this happened. We both missed that SRM, so there was hardly a chance for either of us to find that out.

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      12 years ago, # ^ |
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      I know it's impossible to completely avoid "duped" problem. I'm just a bit surprised.

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12 years ago, # |
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What is the logic behind Div-2 Problem C ??

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    12 years ago, # ^ |
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    just try it out wid some input values and observe the pattern....look for dependencies if any cell is 1..u wil find cells dependent in groups of 4, 2 and 1..so each square of size n gives some 4 pairs, some 2 pair and 1 one. now all possible combinations of sums from these pairs can be reached with square of size n. max sum dat can be reached using square of size n is sum of all pairs of 4, 2 and 1.

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      12 years ago, # ^ |
        Vote: I like it -8 Vote: I do not like it

      Why is the output of x=3 is 5 ..Cant we have something like:

      1 0 0
0 1 0
1 0 0
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        12 years ago, # ^ |
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        it is not symetric.

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          12 years ago, # ^ |
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          Oh..I just read "Let's call matrix A symmetrical if it matches the matrices formed from it by a horizontal and/or a vertical reflection" and skipped the formal description.. From that statement I had made the conclusion that if we place a mirror on the bottom or the right and take the reflection and match then if we get the same array ,Its done..

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          12 years ago, # ^ |
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          y not..

          0 1 0

          0 1 0

          0 1 0

          for x=3...??

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            12 years ago, # ^ |
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            You have adjacent "1".

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              12 years ago, # ^ |
                Vote: I like it -7 Vote: I do not like it

              oh shittt....

              jst got lost with that symmetric thng....

              thnx.

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12 years ago, # |
← Rev. 2   Vote: I like it +13 Vote: I do not like it

The Div1-E has been mentioned on Topcoder before (check SRM 484 Div1-Hard editorial) for reference). EDIT: Too slow

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12 years ago, # |
  Vote: I like it +5 Vote: I do not like it

Like the problem set! e.g., for problem C, after analyzing a bit we can actually come up a very simple DP algorithm. Problem A (the easiest one) is too tricky to trap me for a long time...

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12 years ago, # |
  Vote: I like it +5 Vote: I do not like it

Any one Can tell me the Connection between Problem E with NumberMagic? ( SRM 484 Div 1 1000 ? ..

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12 years ago, # |
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In Div2-C, how does the square look like for x = 3 ?

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    12 years ago, # ^ |
    ← Rev. 2   Vote: I like it 0 Vote: I do not like it 
    0 0 1 0 0
0 0 0 0 0
0 0 1 0 0
0 0 0 0 0
0 0 1 0 0
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    12 years ago, # ^ |
    ← Rev. 4   Vote: I like it 0 Vote: I do not like it

    It can be done in matrix of size 5, but no less.

    00000

    00000

    10101

    00000

    00000

    [Edit:Slow]

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    12 years ago, # ^ |
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    0 0 1 0 0

    0 0 0 0 0

    0 0 1 0 0

    0 0 0 0 0

    0 0 1 0 0

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    12 years ago, # ^ |
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    00100 00000 00100 00000 00100

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12 years ago, # |
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Somebody can tell me the value of n for x = 2 in problem C (div 2) and how the matrix looks like? Thanks.

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12 years ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

I really dint want to do this.But I am facing a strange trouble in the submission of the problem-B of div 2. It gives wrong answer on pretest 11 but when I run the program in my system for the same input it is giving correct answer. Here is the link http://www.codeforces.com/contest/202/submission/1844228

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12 years ago, # |
  Vote: I like it +24 Vote: I do not like it

Excellent contest. It was not very suitable time for me but I don't regret that I tried to compete.

Output format in D was ridiculous (bad that non-Russian speakers won't get it).

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12 years ago, # |
  Vote: I like it +10 Vote: I do not like it

Will it have an editoral?

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12 years ago, # |
  Vote: I like it +3 Vote: I do not like it

FAIL:(
Minor mistakes (less than 5 chars of code each, one per task) in tasks B and C and I am 221th instead of ~90th.
I need to exercise more often.
Good contest anyway!
I have had a lot of fun!

[:||||||||||:]
:-)
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12 years ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

4 a b c d 1 11 b c b a d d d a a c b for this test in B problem i am getting wa when in my pc i am getting the correct ans. code can anybody explain?

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    12 years ago, # ^ |
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    even iam having the same problem. If you get why it is happening please post it here

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12 years ago, # |
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what is test case 11 in Div2 B?

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    12 years ago, # ^ |
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    4

    a b c d

    10

    20 d c c c c c b b b b b a a a a a a a a a

    20 d c c c c c b b b b b a a a a a a a a a

    20 d c c c c c b b b b b a a a a a a a a a

    20 d c c c c c b b b b b a a a a a a a a a

    20 d c c c c c b b b b b a a a a a a a a a

    20 d c c c c c b b ...

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12 years ago, # |
  Vote: I like it 0 Vote: I do not like it

When will editorial be available?

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12 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I didn't understand the definition of "clear" matrix in "Clear Symmetry." "Clear" means that no two or more adjacent "1"s never appear? Thank you in advance.

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