Hello, Codeforces!
The 25th Balkan Olympiad in Informatics takes place in Chișinău, Republic of Moldova, from July 02 (arrival day) to July 08 (departure day) 2017. The most gifted students from the Balkan region of Europe will have the opportunity to prove their knowledge and skills in informatics.
CS Academy will host the online mirrors of both competition days. The first contest starts on Tuesday, July 04, 11:00:00 UTC, right after the onsite competition ends. The round will be rated on CS Academy. The problem statement will be available in English.
Contest format
- You will have to solve 3 tasks in 5 hours.
- There will be full feedback throughout the entire contest.
- The tasks will have partial scoring. The maximum score for each problem will be 100 points.
- There will be no tie breaker, so two users having the same total score at the end of the contest will share the same place in the standings.
If you find any bugs please email us at contact@csacademy.com
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Hope there would be no geometries, And fft, And flow, And...
Well no fft no fun :)
Welp...
In the chat after the contest, someone mentioned using SQRT decomposition to solve the first problem. I know how to use it efficiently for all modification queries, but I'd appreciate if someone could tell me how to do the palindrome check, or just give a hint.
Palindromes can be checked by hashing.
Thanks!
Strings : 2 minutes think, 20 minutes code, 2h debug.
Found a bug in the official solution when upsolving tale. Take case 50: my answer is 294779, the judge answer is 294815, Geogebra sketch shows my answer is correct. I can see where the problem is: it's necessary to compute the overlap area from two circles centered at non-adjacent vertices; only taking adjacent vertices makes the overlap smaller and the judge answer accordingly larger.
I'll inform the organisers too.
UPD: Organisers already know and agree.