You didn't answer my question. Does "library" here mean that you are able to use a hashmap other than the one in std::collections, or not?

When someone fully re-implements khash in Rust and publishes the library, that will become a question which merits consideration.

Meanwhile, from the task description: Please don't implement your own custom "hash table" - it will not be accepted.

So, the answer is "no, you are not allowed." But you're open to changing that. Got it.

Can't use a library that doesn't exist.

If you want an additional Rust hashmap implementation then you need to persuade the Rust community to provide one in std::collections.

No one is allowed to -- in your words -- "write an entirely custom [hashmap] just for the benchmark".

> If you want an additional Rust hashmap implementation then you need to persuade the Rust community to provide one in std::collections.

Again, this means that for Rust, it _has_ to be in the standard library. But C doesn't have one in the standard library. So C gets to write their own, and Rust doesn't.