The Rust code provided runs in 0.1 s (debug) / 0.04 s (release) for me (generic ultrabook + linux). That's quite a lot faster.

Don't think I'm the first to mention - what would profile.release do if you're not calling cargo build --release?

Maybe the author is, but a slight suspicion... they're calling older code.

(Also, what's the deal with read_file() and wanting a Vec<String>? Rust has a read_to_string() method as part of std::fs.)