tbh, I was surprised myself, especially since the Sample Tests by themselves ran quite a bit faster than they do in the Julia version (this detail made me believe the slowness is mostly language related rather than something like the codewars R runner slowing things down).

I'm still relatively new to R, but from what I understand, it is just innately slow along with the added caveat R + for loop = heat death of the universe. Unfortunately, I couldn't find other meaningful areas to use its innate vectorization (which tends to speed things up). Any other idiomatic optimizations I tried gave marginal or no gains while further limiting the readability of the reference solution.

In the end, after quite a bit of tinkering, this is about as fast as I could get it to go. That being said, I can't be certain I haven't missed some other implementation detail particular to R.

It's not fast enough :( I'll need to refactor it if I'm going to pass again.

I tried, it passed as is in 9.x seconds