Rust Program: Company Part 1

Continuing with "The Rust Programming Language" Book Chapter 8.3 homework assignments, this is part 1 of the third problem.

The assignment is: "Using a hash map and vectors, create a text interface to allow a user to add employee names to a department in a company. For example, “Add Sally to Engineering” or “Add Amir to Sales.” Then let the user retrieve a list of all people in a department or all people in the company by department, sorted alphabetically." ... https://www.youtube.com/watch?v=XznBjcl8hOU