Xellos's blog

Invitation to IPSC 2013
By Xellos, 12 years ago, In English

My first blog post, so exciting ^_^

Ehm, the Internet Problem Solving Contest will take place on Saturday 8.6.2013. The practice session lasts 24 hours and ends at 8:00 AM (UTC), while the contest itself starts at 10:00 AM and lasts 5 hours.

The tasks have similar format to CodeJam ones — there is an easy and a hard subtask for every problem, you're given the input data for each subtask and have to submit the output in the format required. Except there's no time limit between downloading the input and submitting, and you aren't required to submit your code (in fact, not even to code anything :D). But there are limits on the number of submissions for each problem!

The problemset consists of standard algorithmic tasks of varying difficulty, as well as some unusual tasks (like a task without a problem statement), tasks touching what you might experience in real life, or interactive ones, where you get feedback for your output and base your next output on this feedback.

The contest uses ACM-ICPC scoring rules, and every subtask is worth 1 point.

There are 2 divisions: open and secondary-school. There is also a separate scoreboard for single-person teams in each division.

I'm sure the contest will be great. Don't miss it!

EDIT: If possible, send a postcard to the organizers. Apart from earning -60 penalty minutes (in case it arrives before the contest), you're enlarging their collection :D

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12 years ago, # |
  Vote: I like it +25 Vote: I do not like it

Just in case, if somebody miss the direct link — http://ipsc.ksp.sk/

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    12 years ago, # ^ |
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    I had the feeling that something was missing! Thanks :D

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

Actually, postcard will deduct 60 minutes (and not earn 20)

This year due to Russian post meltdown we would not send a postcard

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    12 years ago, # ^ |
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    WTF did I just write... yeah, of course. Edited. Still, it'd be nice to have as unusual postcards as possible :D

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12 years ago, # |
  Vote: I like it +17 Vote: I do not like it

Practice problem P2 is fantastic! Had a lot of fun solving it )))

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

Even practice tour seems to be pretty challening! Can't wait for the main contest!

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    12 years ago, # ^ |
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    Exactly. A bit different from standard ACM/ICPC/CF/TC problems.

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12 years ago, # |
  Vote: I like it +13 Vote: I do not like it

Is anybody facing the issue with http://ipsc.ksp.sk/ ?

It looks like it crashed, I can't even ping it

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12 years ago, # |
← Rev. 2   Vote: I like it +5 Vote: I do not like it

is the website down?

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12 years ago, # |
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Right. I wonder what happened... CF anyone? :D I'm sure it's temporary.

UPD: It's working again.

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12 years ago, # |
  Vote: I like it +71 Vote: I do not like it

How to solve H2?

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    12 years ago, # ^ |
    ← Rev. 3   Vote: I like it +8 Vote: I do not like it

    Send HTTP request, with Accept: text/tattoo and play a little game with monster :) Pretty easy.

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    12 years ago, # ^ |
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    Send an HTTP request to the page using the HEAD method. Actually I haven’t even tried other methods, so maybe any method works. Anyway, here’s an example (with extraneous headers removed for brevity):

    HEAD /2013/real/problems/h.html HTTP/1.1
Host: ipsc.ksp.sk

HTTP/1.1 200 OK
H2: A blue monster approaches you and says: "I know the word you need for H2. But I won't talk to you unless you feed me first. I'm in the mood for some dessert... its name doesn't matter, but it must contain chocolate."

    Send a cookie with ‘chocolate’ in the value (if it doesn’t contain ‘chocolate’, you get the same response as before):

    HEAD /2013/real/problems/h.html HTTP/1.1
Host: ipsc.ksp.sk
Cookie: name=chocolate

HTTP/1.1 200 OK
H2: "Yum! All right, if you answer this question, and do it quickly, I'll tell you the answer for H2."
H2-Question: How much is 665 plus 192?
H2-Answer: (your answer)

    You need to resubmit the request with an additional request header H2-Answer: 857. If you try to answer by hand, you’ll get something like:

    H2: "Too slow! Try again!"
H2-Question: How much is 265 plus 29?
H2-Answer: (your answer)

    So you write a program and get:

    H2: "Correct! The word you're looking for is CLASSIFICATION."
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      12 years ago, # ^ |
        Vote: I like it +8 Vote: I do not like it

      In fact, one can submit H2-Answer by hand, but it would be too slow to type the whole request by hand. Using a tool like curl would do.

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    12 years ago, # ^ |
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    First, we make a HTTP HEAD (or HTTP GET) request and read the head of the response. It is the “head of the slave”, because the “slave” is defined here: “problem statement is the slave we sent to you, carrying the secret message”.

    sh$ curl -I ipsc.ksp.sk/2013/real/problems/h.html
HTTP/1.1 200 OK
<...>
H2: A blue monster approaches you and says: "I know the word you need for H2. But I won't talk to you unless you feed me first. I'm in the mood for some dessert... its name doesn't matter, but it must contain chocolate."

    A “dessert with chocolate” is cookies, or, in our case, HTTP cookies. The name of a cookie doesn’t matter, but the cookie itself must contain the “chocolate” substring.

    sh$ curl -b 'some=bbbchocolateaa' -I ipsc.ksp.sk/2013/real/problems/h.html
HTTP/1.1 200 OK
<...>
H2: "Yum! All right, if you answer this question, and do it quickly, I'll tell you the answer for H2."
H2-Question: How much is 93 plus 76?
H2-Answer: (your answer)

    Then we have to compute the answer quickly enough and pass it in H2-Answer HTTP header. If we don’t do it quickly, the response will contain the next question. Otherwise, it tells the correct answer.

    sh$ curl -H 'H2-Answer: 169' -I ipsc.ksp.sk/2013/real/problems/h.html
<...>
H2: "Correct! The word you're looking for is CLASSIFICATION."
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    12 years ago, # ^ |
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    Using wget -S which prints the server response with monster message. Later setting desired headers in this way: wget "--header=Cookie: dessert=chocolate".

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12 years ago, # |
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Shame on team. We couldn't solve J1/J2 — it looks like my boolean algebra lessons made no sense to me. Could anybody explain it?

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

Did anyone else get this for C1?

CHANGE 1607055075 TO 0

then

GE 1704106159 TO 1

then

GE 1 TO 1

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    12 years ago, # ^ |
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    You changed code incorrectly. You inserted z modulo 9 instead of z.

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    12 years ago, # ^ |
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    there must be something wrote on your code, the correct first output is "CHANGE 1607055075 TO 853225920"

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12 years ago, # |
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Preliminary version of the solution booklet has been published: http://foja.dcs.fmph.uniba.sk/ipsc/BOOKLET.pdf

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12 years ago, # |
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Am I the only one who googling this thing "tattooed by Histiaeus on the slave's head" and read some historical paper just want to know what word that writen in Histiaeus slave's head because you think the answer is like that ?

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    12 years ago, # ^ |
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    We thought in exactly the same way.

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      12 years ago, # ^ |
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      So what? Get that message? :-D

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        12 years ago, # ^ |
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        No. You can find correct solution above. Answer is not guessable.

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          12 years ago, # ^ |
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          That was me, who answered first to your question above :)

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    12 years ago, # ^ |
    ← Rev. 2   Vote: I like it +17 Vote: I do not like it

    I also read about it and then tried to submit "REVOLT" but it gave me a Wrong answer :D You can expect anything from a contest whose practice contest contained a Pokemon national No. :D:D

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    12 years ago, # ^ |
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    Nope you weren't :-) I thought the answer was REVOLT.

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12 years ago, # |
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How to solve D?

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    12 years ago, # ^ |
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    I'm sorry, that was not in English. And now my English is not good.

    d1. dp[mask] — — maximal answer for permutation of letters in mask answer is final position of pointer in greedy algorithm of collecting letters from string. if dp[mask] <= n, all is OK.

    d2 is interesting for me too.

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      12 years ago, # ^ |
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      yeputons done like this.

      Lets count permutations which are in string. This can be count using brute-force. If stop when we have letter, we can't got it works in several minutes.

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