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Discussion of Problem 2099. Space Invaderroman velichkin Is it possible to get wrong answer because of rounding numbers? [1] // Problem 2099. Space Invader 5 Oct 2023 13:50 Vectors calculations uses square roots. Could this lead to not very precise floats and wrong results? Edited by author 05.10.2023 13:50 Edited by author 05.10.2023 13:50 Vedernikoff 'Goryinyich' Sergey (HSE: АОП) Re: Is it possible to get wrong answer because of rounding numbers? // Problem 2099. Space Invader 6 Oct 2023 17:43 In this sort of problems rounding errors could be the source of problems. That's why you shall avoid using float types here. The problem is completely solvable in integers. die_young WA5 [2] // Problem 2099. Space Invader 30 Jul 2018 23:38 Check that you indeed turn after reaching point B, i.e. that intersection point is not between A and B or you don't even reach B. roman velichkin Re: WA5 [1] // Problem 2099. Space Invader 5 Oct 2023 13:45 There is something else. My code checks turning before B but still got WA on #5. roman velichkin Re: WA5 // Problem 2099. Space Invader 5 Oct 2023 14:21 Spaceship can go only forward, so check - there shouldn't be any backward movement. Test #5 is about that. Edited by author 05.10.2023 14:33 Ade WA9 // Problem 2099. Space Invader 25 May 2023 20:35 a-b and c-d are close, but not touching each other. -2 0 0 -1 0 0 0 1 0 0 1000000 1 andreyDagger WA1 // Problem 2099. Space Invader 15 Feb 2022 16:09 Spend 10 submissions to realise, that I don't return anything from function, that must return bool value Toshpulatov (MSU Tashkent) test // Problem 2099. Space Invader 22 Dec 2020 17:59 0 0 0 1 0 0 2 1 1 2 2 1 ans Invalid Совет для тех кто решает векторами, лично у меня не получилось сдать задачу векторами, пришлось писать уравнения прямой в пространстве Mahilewets Instruction how to solve. [2] // Problem 2099. Space Invader 3 Jun 2017 17:51 Check (AB,CD)==0 (orthogonality). Check (AB, CD, DA) ==0 (planarity). Check AD>AC>AB, AC>BC, BD>BC (order). Check whether the projections to XY, YZ, XZ craddle each other continuations. It is sufficient to check only the projections to XY plane to get Accepted verdict. ARK (***AESC_USU***) Re: Instruction how to solve. // Problem 2099. Space Invader 26 Dec 2017 04:29 Sounds too complex. If we replace C, D with their orthogonal projection on AB, then all steps except first collapse to only one step (check D = C*a, a > 1). Still too complex, though. Over 20 lines in Python. There should be more simple solution... Edited by author 26.12.2017 04:30 ASK Re: Instruction how to solve. // Problem 2099. Space Invader 15 Mar 2018 19:04 No lengths or projections XY, etc. Using scalar product (sp) and triple product (tp) it is at most five conditions: sp(ab,cd) == 0 and tp(ab,bc,cd) == 0 and # ⟂ and planar sp(ab,bc) >= 0 and # C after B sp(cd,bc) >= 0 and # BC goes in direction of CD sp(cd,bd) >= sp(cd,bc) # D after C liudy Wa #13 [1] // Problem 2099. Space Invader 13 Aug 2016 08:45 Can someone tell me what the test#13 example please? Mahilewets Re: Wa #13 // Problem 2099. Space Invader 3 Jun 2017 17:53 Something like AB and CD are orthogonal and complanar and there is no right such point E, that E lies on AB-line, E lies on CD line and the angle AED is ninety degrees.
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