clever, I had same solution but did n * -1 instead of just -n. Good idea

This is clean and simple.

It's been a minute, but if you're still interested, try looking up "method groups".
They are essentially a way of telling the compiler: 'Hey, here's the name of a method with multiple overloads, please find the one with the correct signature for this scenario'.
At least that is my probably flawed understanding.

What am I looking at?

Nice, using hash set! Using a hash set for checking an element existence in a collection is the fastest way, but because the vowels characters are just a few, an array or list may suffices.

yes

@jamescurran:
I rephrased my comment to be simpler and more precise.

Amazing solution!

Could you please explain why is that?

OK, I used a stack to solve the question, but this is much better since it requires only O(1) of extra space! Kudos!

I like the use of Func, makes the whole thing really concise. The only thing I don't like about this, is that you iterate through each array twice, where once would suffice.

I am trying to come up with a way to do that using "getMinMaxLength Func<string[], Tuple<int, int>>", where you find the min and max in one iteration. I am not yet familiar enough with lambdas in C# to get it right without thinking longer about it. Do you know how?