I love how this beauty received 26 Best Practises upvotes, and 8 clever ones.
Too bad you have to choose: it's clearly both.

Water Rat (me, nice...) solved this thing in the year of the Wood Dragon.

My advice is to look into 'type coercion' and while you're at it, 'type conversion' and figure out the difference. It's quite interesting stuff.

GO sounds so special that I'm not even going to try.

Having my hands full anyway with struggling through 120,000 lines of DXL code, written by even more incompetent programmers than I am, at work.

Sorry, but I had to get that of my chest. ;-)

Dont mind me.

I got the same and "solved" it by including \t as an acceptable character. It's a bit weird.

My brain must be myjinxined after solving a few hundred of his Kata's.
I perfectly understood what he meant. :-D

It's not pretty, I know.

I'm sure this can be solved with some kind of smart bitwise magic.
And I'm also sure that I'm not smart enough to figure this out.

One of the earlier Kata's. Nowadays this thing would have been rated an 8kyu. ;-)

is that an order?

While trying to solve: "Wow, this is a lot harder than I thought"
After solving, looking at the top-solution: "Oh, yeah, alright..."

This is a thing of beauty.

Yeah, it's a six at least. My best guess is that people ranking kata's are mostly high ranks that tend to underestimate difficulty.
I've solved 4kyu's that were easier than this one.

Just what I thought.
I'm an idiot.

I think there's a O(2n) or even O(n) solution, but the test cases are not really helpful to verify my ideas.