For those attempting this Kata without outside help, assuming all points are part of the hull and then reducing them is the WRONG approach. It will work, but it's not performant enough (at least for some languages) and you will time out.

Python submission Attempt test cases are all failing; the input and output are switched places.
I copypasted them to my own tests: they pass, the test data itself is ok.

Meanwhile the given Sample tests are working correctly.

Last line of the kata: The array will never be empty.

Also 8th kyu kata are introductory, so error handling would be too advanced for this kata.

Doesn't handle:

• empty list
• bad data where list has elements of None

Thank you for this interesting Kata!

Elixir translation.

Oh, that makes a lot of sense! Thank you.

The test solutions have been sorted to account for differing methods and starting vertices

Hey guys, regarding the Haskell translation, in one of the hardcoded tests it expects a hull of [(1.0,20.0),(5.0,6.0),(6.0,20.0),(15.0,19.0),(19.0,4.0),(20.0,4.0)], which doesn't make sense...? Going from first to second to third means turning left, and from second to third to fourth means turning right, but should't we only turn in the same direction? Or am I missing something?

Hey Blind4Basics, I don't want to offend you personally and so would I urge you not to either. But I'll describe what made me downvote yesterday.

So, you're the kind of guy who downvote the other one who tries to help you? Maaaaaan, that's pretty fair, don't you think? Especially when that guy isn't even the author of the kata or the translation and just take on his time to help you...

FYI, I just checked again, and the solution I used to replace the original one returns your """real convex hull""" as it should. So I don't know what is the problem, but I'm sure of one thing: this time it's on your side. I just changed one thing more, so that the expected value is computed before your function even touches to the data... Just in case you're actually mutating the input without even thinking about it and then reject the fault on someone else...?

Have you reset the kata? The current reference solution returns the second array ("real convex hull" as you call it).

okay let me emphasize that every randomly generated testcase has a wrong solution. Here you have another example:
([points],[given solution],[Real convex hull]):
([[96, 56], [48, 33], [17, 73], [57, 7], [14, 17], [31, 46], [54, 47], [48, 95], [89, 96], [75, 15], [96, 87], [33, 69], [17, 41], [76, 97], [75, 99], [77, 20], [57, 52], [90, 41], [96, 83], [42, 26], [66, 84], [26, 33], [28, 45], [59, 76], [44, 9], [45, 53], [22, 33], [31, 62], [31, 94], [49, 92], [76, 60], [40, 37], [41, 70], [98, 18], [29, 78], [80, 25], [60, 6], [81, 56], [82, 24], [56, 26], [16, 83], [88, 75], [57, 9], [62, 7], [72, 12], [93, 48], [24, 79], [97, 17], [27, 41], [91, 44]],[[14, 17], [16, 83], [31, 94], [44, 9], [60, 6], [75, 99], [89, 96], [96, 87], [97, 17]],[[14, 17], [16, 83], [31, 94], [44, 9], [60, 6], [75, 99], [89, 96], [96, 87], [97, 17], [98, 18]])