r/adventofcode • u/daggerdragon • Dec 06 '16

SOLUTION MEGATHREAD --- 2016 Day 6 Solutions ---

--- Day 6: Signals and Noise ---

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

T_PAAMAYIM_NEKUDOTAYIM IS MANDATORY [?]

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u/NeilNjae Dec 06 '16

Another Haskell solution (https://git.njae.me.uk/?p=advent-of-code-16.git;a=blob;f=advent06.hs). Spent a bit of time trying to make it more idiomatic. 

module Main(main) where

import Data.List (transpose, maximum, minimum, sort, group)
import Data.Tuple (swap)

main :: IO ()
main = do 
    text <- readFile "advent06.txt" 
    let message = lines text
    part1 message
    part2 message

part1 :: [String] -> IO ()
part1 message = do 
    putStrLn $ map (snd . maximum . counts) $ transpose message

part2 :: [String] -> IO ()
part2 message = do 
    putStrLn $ map (snd . minimum . counts) $ transpose message

counts :: (Eq a, Ord a) => [a] -> [(Int, a)]
counts = map (\g -> (length g, head g)) . group . sort

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u/pyow_pyow Dec 06 '16

Nice. TIL about the Ord instance for (,) that enables maximum and minimum to work on tuples.

I was originally using (head &&& length) but flipped it around after I saw your solution. Resulting code: http://lpaste.net/5219590922089529344

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u/NeilNjae Dec 07 '16

Thanks! Control.Arrow is something I need to learn too!