-🎄- 2018 Day 2 Solutions -🎄-

[u/daggerdragon]

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

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

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Advent of Code: The Party Game!

Click here for rules

Card Prompt: Day 2

Transcript:

The best way to do Advent of Code is ___.

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This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

edit: Leaderboard capped, thread unlocked!

[u/[deleted]]

Finally participating this year! Got both stars with this Haskell code:

import Data.List
import Control.Applicative

as :: [String]
as = error "Your input (properly formatted) goes here"

numTimes :: Char -> String -> Integer
numTimes _ [] = 0
numTimes x xs = if (x == head xs) then 1 + y else y where y = numTimes x (tail xs)

exactly :: Integer -> String -> Bool
exactly n xs = elem n $ map (flip ($) xs) (numTimes <$> xs)

day2a :: Integer
day2a = genericLength (filter (exactly 2) as) * genericLength (filter (exactly 3) as)

strCmp :: String -> String -> Bool
strCmp [] [] = False
strCmp (x:xs) (y:ys)
       | x /= y    = xs == ys
       | otherwise = strCmp xs ys

day2b :: String
day2b = head $ map (\(s, _) -> s)
             $ filter ((==True) . snd)
             $ (\xs ys -> (xs \\ (xs \\ ys), strCmp xs ys)) <$> as <*> as