

Day 19 is definitely my proudest solve (though learning about Aho-Corasick dampens it a little bit 😅) with some clever ideas to both check towels more efficiently than the naïve approach while creating no String
s to avoid a bunch of heap allocation. Figuring out how to binary search without creating the target object, and merely knowledge of its properties and those of the list, meant I got to use a pretty niche library function and got my solution from 25 to 11 ms.
Rust
Definitely not Aho–Corasick cool or genius, but does get ~11ms on both parts. Gains over the other Rust solves are partly a less naïve approach to towel checking and partly getting it to work with 0
String
allocations, which involves both an instructive lifetime annotation and the clever use of a niche standard library function.Code