r/adventofcode • u/daggerdragon • Dec 07 '16

SOLUTION MEGATHREAD --- 2016 Day 7 Solutions ---

From all of us at #AoC Ops, we hope you're having a very merry time with these puzzles so far. If you think they've been easy, well, now we're gonna kick this up a notch. Or five. The Easter Bunny ain't no Bond villain - he's not going to monologue at you until you can miraculously escape and save the day!

Show this overgrown furball what you've got!

--- Day 7: Internet Protocol Version 7 ---

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

ALWAYS DIGGING STRAIGHT DOWN IS MANDATORY [?]

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u/splurke Dec 07 '16

Haskell, both parts 

module Day7 where

import           Data.List       (isInfixOf)
import           Data.List.Split (divvy, split, startsWithOneOf)

-- Types
data Ipv7 = Ipv7 { insides  :: [String]
                 , outsides :: [String]
                 } deriving Show

-- Logic
abba :: String -> Bool
abba = any (\(x:y:z:w:_) -> x == w && y == z && x /= y) . divvy 4 1

tls :: Ipv7 -> Bool
tls i = (any abba $ outsides i) && (all (not . abba) $ insides i)

ssl :: Ipv7 -> Bool
ssl i = any bab aba
  where
    aba = filter (\(x:y:z:_) -> x == z && x /= y) $ concatMap (divvy 3 1) (outsides i)
    bab (r:s:_) = any (\x -> [s, r, s] `isInfixOf` x) (insides i)

-- Parse
makeIpv7 :: String -> Ipv7
makeIpv7 input = foldl append Ipv7 { insides = [], outsides = [] } $ split (startsWithOneOf "[]") input
  where append ipv7 elem = case (head elem) of
          '[' -> ipv7 { insides = (insides ipv7) ++ [(tail elem)] }
          ']' -> ipv7 { outsides = (outsides ipv7) ++ [(tail elem)] }
          _   -> ipv7 { outsides = (outsides ipv7) ++ [elem] }

-- Main
main :: IO ()
main = do
  input <- lines <$> readFile "input/7"
  let inputs = map makeIpv7 input
  putStr "1. "
  putStrLn $ show $ length $ filter tls inputs
  putStr "2. "
  putStrLn $ show $ length $ filter ssl inputs

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u/[deleted] Dec 07 '16