aoc-2021/07_day/code.hs

import Data.List

splitStrOnce :: String -> String -> (String, String)
splitStrOnce separator "" =  ("", "")
splitStrOnce "" subject =  (subject, "")
splitStrOnce separator subject = do
    let sepLen = length separator
    if (take sepLen subject) == separator then
        ("", (drop sepLen subject))
    else do
        let res = splitStrOnce separator (tail subject)
        (((head subject):(fst res)), (snd res))

splitStr :: String -> String -> [String]
splitStr separator "" = []
splitStr separator subject = do
    let res = splitStrOnce separator subject
    (fst res):(splitStr separator (snd res))

intOfString :: String -> Int
intOfString x = read x :: Int

minimumsSnd :: Ord b => [(a, b)] -> [(a, b)]
minimumsSnd [] = []
minimumsSnd xs = filter ((==) minsnd . snd) xs
    where minsnd = minimum (map snd xs)

sumK n = ((n+1)*n) `div` 2

main :: IO ()
main = do
    input <- getContents
    let crabs = do {
        map (\x -> read x :: Int) $
        map (filter (\x -> x /= '\n')) $
        splitStr "," input
    }
    let cases = do {
        map 
        (\x -> (x, sum (map (\y -> sumK (abs (y-x))) crabs)))
        [(minimum crabs)..(maximum crabs)]
    }
    let min = minimumsSnd
    putStrLn $ show $ snd $ head $ min cases -- ans to part 2

-- Gross, but it works