One thing to note about #AdventOfCode: It is really, really important to inspect your input data.

Your data could be considered part of the puzzle description. By inspecting it, you can find clues and you might find out that you can make certain assumptions.

(I mean, what’s the alternative? There could be a list of allowed assumptions in the textual descriptions, right? That wouldn’t be a lot of fun, I think, as it would give away too much information about the solution. It’s more interesting to find those clues yourself.)