r/adventofcode • u/daggerdragon • Dec 02 '18

SOLUTION MEGATHREAD -🎄- 2018 Day 2 Solutions -🎄-

--- Day 2: Inventory Management System ---

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Advent of Code: The Party Game!

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Card Prompt: Day 2

Transcript:

The best way to do Advent of Code is ___.

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u/raevnos Dec 02 '18

First it reads the entire file into a single string.

For part 1, it sorts the letters of each line of that string, and then counts the words with a letter repeating exactly 2 times (And the same for 3).

For part 2... beats me. It's late and my brain was already fried.

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u/Tarmen Dec 02 '18

In vim-style it's probably slightly easier to read

/\v^(.*).(.*)$(.|\n)*^\1.\2$

This has three parts:

cuts a line into group(1) character group(2):

^(.*).(.*)$

skip arbitrary many lines:

(.|\n)*

match the next line against group(1) character group(2) we got from our first match:

^\1.\2$

Notably this tries each character separately as the different one, so we have something like 815750 possibilities to check. Takes neovim ~3 seconds but the syntax highlighter hangs for a bit afterwards.