After spending all day trying to make a few of these better, I wasn’t able to. I spent most of that time on symmetric difference trying for a different solution.
For phone numbers, the hard part was getting the magic regex. For exact change, I couldn’t see a way to consolidate all the while loops.
These were more difficult but, I thought, less interesting than the intermediate ones.
Here’s the third set of algorithm problems.
I’ll start uploading the projects I’ve finished next.