AoC 2020 - Day 1: Report Repair

I actually forgot about AoC, this year, so I started it late. Anyways, here I am; this year I will also try to comment all my solutions as soon as they are ready, and publish them on Github before the end of the day.

So, today’s task was quite a typical interview coding task, with just some story about Christmas (small OT: I really hope we are going to save Santa again!).
This was one I was fully prepared, having done it countless times; but I suspect that the second part, without an efficient first part, could have taken a bit too much time.