It might be unpopular to say this but: can we please stop teaching people to write new programs in C? The language is inherently unsafe, and we're collectively losing billions of dollars per year to preventable memory safety errors.
Why not use Rust or C# or something to demonstrate the principles of hash tables? Why start with the programming equivalent of a 1950s death crap automobile with a spike in the center of the steering wheel?
If a new hire is minimally competent at programming, I can bring them up to speed in whatever language it is we are using. Hell, even when people have notionally been taught a language in school, there's a decent chance I would still have to train them in that language as a new hire, because what they learned in school may be insufficient to cover the complexities that get involved in practice.
And to OP's point: C itself is a pretty poor language at covering what it actually covers. It has some missing features that just seem random (e.g., there are no 8- or 16-bit arithmetic operators in C). It has gratuitous undefined behavior (signed integer overflow and strict aliasing). As a language design, it's atrociously outdated (#include is a very poor substitute for modules, and generic programming might as well not exist in C). There are questionable features--null-terminated strings don't look like such a good idea in retrospect. Even if you want to avail yourself of its strengths--access to low-level hardware features--C's gratuitous undefined behavior (particularly strict aliasing) undercut it there, and languages like Rust and Zig give you the same power with none of C's warts.
C's job is to be the first thing ported to a new architecture, allow you to bootstrap a system, and build on top of it (last 2 steps optional if you're working on some sort of embedded system).
And, frankly, it's reasonably good at that. Writing a simple C compiler is trivial compared to something like rust.
[1] https://github.com/rust-lang/rust/tree/master/compiler/rustc...