Ah, I understand that part, but I assumed they were looking for the most ergonomic/succinct and idiomatic approach (ie not needing to reach for a crate). But it

Ah, I understand that part, but I assumed they were looking for the most ergonomic/succinct and idiomatic approach (ie not needing to reach for a crate). But it doesn't have the same performance characteristics as using itertools (which is better here)