In this exercise I am using Visual Studio 2019 and a modified version of the std_lib_facilities header found here.
Chapter 23 // Exercise 2
Add a multimap and have it hold subjects. Let the program take an input string from the keyboard and print out every message with that string as its subject.
2 months after starting this chapter I had almost forgotten everything and this took me longer than expected.
The hard part had already been provided by Bjarne though so it was just a case of creating a new multimap that stores messages and subjects and loops through that instead if there is a match.
