Killing Gs - WA

Hello coders,

my idea how to solve Killing Gs problem (CKROACH) from May 2012 Long contest was to generate random permutations of N integers (k_1, …, k_n) and using just first few insecticides to get probability that Gs_i is dead with probability above 90%. But my submission is getting WA, any idea why?

I believe that this formulae holds: When k_1, …, k_m are indexes of used insecticides, than probability that Gs_i is alive is

p_i = product(j=1;m;1.0-P_{k_j,i}/100.0)

so I’m looking for such min m, that p[i] <= 0.10 for all i.

as far as i know, this formula seems to be correct, as it is directly derived from the problem statement. the mistake here is probably a glitch in your implementation, or related to the way you input/output the result of your computations… i don’t know. you should check your code on several test cases to spot the corner case (if there is one).

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I skipped this condition:

The second line should have K integers, the numbers of insecticides which Ciel buys, in ascending order.


i think this question was N-P completeness question

First I thought that problem is in double aritmetics (rounding or something), but when I tried BigDecimal (Java) I’m getting WA still.

I tried to use generator ( for testing, but my results are correct according to above formulae…

or related to the way you input/output the result of your computations…


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Yes, it is. Setters use such problems as tie break problems. We have to find as good solution as it’s possible in given timelimit, but my was wrong according to wrong output format…

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