abistrigova's blog

XVII Opencup , Eastern GP
By abistrigova, history, 10 years ago, In Russian

How to solve K, C?

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How to solve L?

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    First, check what if a = 0 or c = 0

    then if b is max and it's equal to F_{i+1} then D = b2 - 4ac = (Fi + fi - 1)2 - 4fifi - 1 = (fi - fi - 1)2 that is usually greater than 0, and zero if fi = fi - 1 i.e i = 2

    otherwise D < 0 and there's no solutions.

    fi2 - 4fi + 2fi + 1 < fi2 - 4fifi < 0

    fi2 - 4fi + 1fi - 1 = fi2 - fi + 1fi - 1 - 3fi + 1fi - 1 =  ± 1 - 3fi + 1fi - 1 ≤  - 2 < 0

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Which C? It is better if organizers do not name different tasks with same letters.

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G. How did you solved it?
After splitting to sentences I tried to grep them with regex, but got TLE 29 (ideone).
Then tried use hashes, but failed on TC#3 (give a hint). Can't overcome it in two ways: 1) take each sentence as a hash key, which value is a hash of lowercased words;(ideone) 2) each word from sentences is lowercased and is a hash key, which value is an array of indices of an array of sentences.(ideone).
Later improved(maybe) regex solution with lookaheads, but there is no Upsolving for Div.2 :/ to test if it pass time limits (ideone).

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