Advent of Code 2020 - Day 3

42nd on part 1; 15th on part 2. About 40 seconds behind this time.

This is a basic grid problem. I have a set of conventions I always use for grid problems; the dimensions are "rows" and "columns", indexed by variables named "r" and "c". The upper-left corner is (0,0). Rows increase down and columns increase to the right. Rows are always the first index. i.e. always G[r][c] never G[c][r].

I think it's helpful to have something like this in mind. It doesn't have to be the same as mine; another common choice is x and y with y increasing up. Otherwise you have to think through all these decisions, which costs time and increases the chance of mistakes. I was lucky in this case that my conventions lined up with the problem statement.

[ryancastner]

Honestly the 40s are coming from typing fileimport readlines boilerplate, most people have that already setup I would imagine. I get not every puzzle can use that but most conform to that pattern.

[linlasj]

I love these videos. I am learning something useful all the time!

[robinosolava]

Thanks for these videos and explanations

[kiriappeee]

Thanks for the video and explanation. I like completing the puzzle and then comparing my solution to yours. I don't come from a competitive background so there are going to be obvious approaches I miss and in this case, I actually generated the arrays if I landed in a "chunk" which doesn't exist yet — trying to take a chapter from game chunk generation there 😅.

Pretty neat to see the '%' approach. Is the idea of a repeating pattern like this something you've seen in the past or did you realise on the fly that you could use a mod approach? Just curious because I'm keen to learn what patterns show up commonly in these kinds of puzzles :)

[prestonnewton]

i know you get the same list in the end, but you seem to prefer appending than doing a read().splitlines() for the input file. any reasoning or just your preference?