Advent of Code

2021 was me learning Ruby. 2022 is me getting back into Python.

Notes

@classmethod is handy to make things testable
Use pytest and write simple unit tests as I go along so I have confidence about the utility methods

Other code niceties are _private_methods (a convention) @property and from functools import cached_property
Good tests really sped this up, but

Edge conditions not present in test data floored me repeatedly. When I refactor it's important that tests catch new errors
Are regexes simpler/better than raw indexes?
[::-1] looked cryptic, but is just the [start:stop:step] and reverses the list
I needn't have kept the crate's [ & ], that caused trouble printing
A mixture of proper debugging and printing was useful, would a to string function have been used in the debugger's output?

Use dirs = [] + self._sub_dirs to avoid taking a second pointer to self._sub_dirs.
I can use if file_match := re.match('(\d+) (.*)', row) instead of file_match = re.match('(\d+) (.*', row) then if file_match:.
There are two edge cases that don't get exercised by the test data nor the real data. Almost everybody's solution fails the first one (mine included) and most fail the second. Should I be basing things on the data more than the question itself?
- $ cd / should take you back to the root from wherever you currently are
- Revisiting and ls in the same directory twice should not double its size!

100% coverage is satisfying
Part 2 was not accessible for visually impaired programmers
We should not be committing input files (reddit thread). That'll be a good excuse to look at sub-repositories
- Took the opportunity to combine my 2021 and 2022 repositories (following this SO answer using the allow-unrelated-histories).
- Used git's submodule feature to move all the copied AoC inputs (test and real) to a private repository.
Calling Monkey.bored_with picks the instance method not the class method of the same name!

Part 2 was hard. The breakthrough for me was throw['item'] %= self.product which was a result of me realising it was mathematical (from a comment on reddit).

Remember in or to negate first when tacking second if needed
Passing logic tests and functions (e.g. stop_test and neighbours_func) would have made refactoring straightforward, but may have been premature complexity. Anyway it was easy to fix.
If Eric had not made the Part 2 data take soooo long on the naive solution I would never have fixed it!

Writing logging.info statements to reproduce Eric's explanatory test is a useful additional test if the algorithm passes on the test data but fails on the 'real' data (see reddit thread)
Lots of my time is wasted with sloppy writing, e.g. [i for i in range(self.sorted_packets) if self.sorted_packets[i] in self.divider_packets.contains] instead of [i + 1 for i in range(len(self.sorted_packets)) if self.sorted_packets[i] in self.divider_packets]

extend instead of append adds the items in the list. No need to worry about how to flatten.
To use the capfd fixture pass it into the test function, then call out, _ = capfd.readouterr() to get stdout after the print statements.

Note to self — do not forget to uses square brackets for loc and iloc in pandas, i.e. self.grid.loc[y].value_counts()['#'] not self.grid.loc(y).value_counts()['#']
Cute way using double comprehension to get all pairs [(s1, s2) for i, s1 in enumerate(self.sensors) for s2 in self.sensors[i + 1:]]
I should have taken a geometric approach to the algorithms from the start. I may need to be more on top of geometric algorithms for SVG work anyway. Some interesting solutions at:
- jakesco Part 1 (GitHub)
- JakubDotPy Part 2 (GitHub)
- RGodlike Comparison of different approaches (Reddit)
- appus3r Can't think of an approach (Reddit)
- Ayman4Eyes No search formula (reddit)
- Day 15 Solutions Megathread (reddit)
  - codertee (Github)
  - olliemath rotates the coords to get squares (Github)
  - msschmitt merging ranges (Reddit)
  - zniperr border checking code (Reddit)

mebeim's solutions are very useful since he includes a walkthrough of the code and his thinking