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Обсуждение задачи 1766. Шалтай-Болтай

What's the magic in #18
Послано Ade 5 апр 2013 23:35
Always WA at #18
I gave it everything I have.
Resolve the formula group. Iterate to 1e-15. Still WA.

Any hints?
Thanks

Edited by author 05.04.2013 23:37
Re: What's the magic in #18
Послано Vedernikoff 'Goryinyich' Sergey (HSE: АОП) 6 апр 2013 04:35
Iterative schemes are unstable (small deviations from equilibrium in neighbor nodes lead to large error in final solution), so stupid iteration is hard to get AC here.
Better reduce the problem to linear system and solve it honestly, or reduce it to matrix multiplications (even in this case you need some streetmagic to beat accuracy!)
Re: What's the magic in #18
Послано Ade 9 апр 2013 14:18
Thanks, Vedernikoff

I resolved the linear formulations, but WA#18.
Then I add some iterations afterward to 1e-14. Still failing.

I'm now planning to pure iterations. The initial state doesn't matter, I think. So I'm gonna start from 1/64 in every cell.