Say you have a list like this:
[1, 1, 2, 3, 3, 3]
And you want to find all duplicates in a separate list. In this example:
You can utilize the return value of the Set#add...
There are a million ways to extract values from a string in Ruby. The easiest way that I found and that I constantly use is the  operator together with capture groups.
Take for example the...