https://users.rust-lang.org/t/to-string-vs-to-owned-for-string-literals/1441/5

It looks like they have the same performance

Will compilator optimize for _ in 0..count { ... } to simple let mut i = 0; while i < count { ...; i = i + 1; }?

It is for "n < 3" cases, where extend causes reallocation with capacity 3.

Ah, that's a good point, thanks! I'm too lazy to update the solution though :P

It is better to use to_owned instead of to_string, because it exists precisely for this .