This one is concise and well-understandable, respect!

Thank you for this! This is what I wanted to do but didn't know how to do, so had to longhand it. This is very neat, thanks for teaching me

Условие очень непонятно...

Very good job, we learn a lot in this solutions sections.

I tried my best to get [X, Y] as a result, but in the end I was just required to get Y

very dirty explanation

Approved

python new test framework is required. updated in this fork

This is good job!

I am not sure where Codewars rules say thay you need to be as fast as possible :)

i mean, codewars is sbout doing it as fast as possible, even if its extremely ugly

Oh boi, I really wanted to flex with those one liners the first time I saw them.
Seems like I'm on the right path to get all the girls.

Since every character in the string has to be touched, assuming 'n' refers to the size of 'aeiouAEIOU' -> 10

String comparison method:

vowel, equal frequencies: 5.5 checks

not a vowel: 10 checks, constant

Set, assuming underlying b-tree has minimal depth:

vowel, equal frequency: 1 * .1 + 2 * .2 + 3 + .4 + 4 * .3 = 2.9 checks

not a vowel: upper bound of 4 checks, lower bound 3 checks

Comparing: vowel 5.5 vs 2.9 -> ~1.90 faster for set

not a vowel: 10 vs 3 to 4 -> 3.33 to 2.5 times faster, in theory

Note: this is in theory, the python interpreter and execution environment could make this worse or better

Obviously as 'n' gets (not much) larger, the set is going to be faster. For n = 10, I would say tradeoff is speed versus speed of coding

Can someone please explain what is happening here?
And why the time complexity of this solution is O(n)?