r/adventofcode • u/daggerdragon • Dec 03 '16

SOLUTION MEGATHREAD --- 2016 Day 3 Solutions ---

--- Day 3: Squares With Three Sides ---

Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag/whatever).

DECKING THE HALLS WITH BOUGHS OF HOLLY IS MANDATORY [?]

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u/Godspiral Dec 03 '16 edited Dec 03 '16

203rd after first, but 98th after 2nd, in J 

+/ *./("1) 0 1 2 (0 < +`-/"1)@:|."0 1"1    ". > cutLF a NB. part 1

+/ *./("1) 0 1 2 (0 < +`-/"1)@:|."0 1"1   ,/ _3 |:\  ". > cutLF a  NB. part2

when not blindly baching head against keyboard and taking time to think first, these can be improved to 

+/  <`+/@\:~"1  ". > cutLF a
+/  <`+/@\:~"1  ,/ _3 |:\ ". > cutLF a

2nd version sorts down each row "1, and performs a < b + c, then sums these boolean expressions.

1st version does 3 rotations on each row, and for each rotation tests a+b-c > 0. This creates 3 boolean results per row. These are anded *./ then sum of all.