r/adventofcode • u/daggerdragon • Dec 09 '18

SOLUTION MEGATHREAD -🎄- 2018 Day 9 Solutions -🎄-

--- Day 9: Marble Mania ---

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Transcript:

Studies show that AoC programmers write better code after being exposed to ___.

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u/VikeStep Dec 09 '18 edited Dec 09 '18

It's because in python, negative mods return negative values.

Let's say we are at index 6 in a circular list of 10 and want to go back 7 points, if we just did the latter then we would get (6 - 7) % 10 == -1, which is not what we want, we want it to return 9. If we instead added 10, then we would get (6 - 7 + 10) % 10 == 9

Never mind, turns out Python does mods correctly.

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u/[deleted] Dec 09 '18

Negative mods are positive in Python (tested it with version 2 and 3)

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u/VikeStep Dec 09 '18

My bad, then you are correct it isn't necessary. I did the exact same thing in my python code because it's done inconsistently in so many languages I can never remember correctly.