60 lines
1.8 KiB
Haskell
60 lines
1.8 KiB
Haskell
{-# LANGUAGE OverloadedStrings #-}
|
|
{-# LANGUAGE ViewPatterns #-}
|
|
|
|
import Data.Char (isDigit)
|
|
import Data.List (elemIndex, sort)
|
|
import Data.Maybe (fromJust)
|
|
import Data.Text (Text)
|
|
import qualified Data.Text as T (filter, init, lines, null, span, tail, uncons)
|
|
import qualified Data.Text.Read as T (decimal)
|
|
import Lib (readFile')
|
|
|
|
main :: IO ()
|
|
main = do
|
|
input <-
|
|
map (fst . parse (List []) . T.init . T.tail) . filter (not . T.null)
|
|
. T.lines
|
|
<$> readFile' "day13.in"
|
|
putStr "Q1: "
|
|
print $ q1 input
|
|
putStr "Q2: "
|
|
print $ q2 input (List [List [Elem 2]]) (List [List [Elem 6]])
|
|
|
|
q1 :: [List] -> Int
|
|
q1 input =
|
|
foldl
|
|
(\xs x -> xs + if input !! (2 * x - 2) < input !! (2 * x - 1) then x else 0)
|
|
0
|
|
[1 .. length input `div` 2]
|
|
|
|
q2 :: [List] -> List -> List -> Int
|
|
q2 input a b =
|
|
let sorted = sort (a : b : input)
|
|
a' = fromJust $ elemIndex a sorted
|
|
b' = fromJust $ elemIndex b sorted
|
|
in (a' + 1) * (b' + 1)
|
|
|
|
data List = Elem Int | List [List] deriving (Show, Eq)
|
|
|
|
-- is this cheating :P
|
|
instance Ord List where
|
|
compare (List xs) (List ys) = compare (reverse xs) (reverse ys)
|
|
compare (List xs) (Elem y) = compare (List xs) (List [Elem y])
|
|
compare (Elem x) (List ys) = compare (List [Elem x]) (List ys)
|
|
compare (Elem x) (Elem y) = compare x y
|
|
|
|
-- Weak parser but it works
|
|
-- I do not really know how to use Parsec and ReadP with Data.Text yet
|
|
|
|
parse :: List -> Text -> (List, Text)
|
|
parse (List xs) txt
|
|
| T.null txt || cur == ']' = (List xs, rest)
|
|
| cur == '[' =
|
|
let (new, next) = parse (List []) rest
|
|
in parse (List (new : xs)) next
|
|
| isDigit cur = parse (List (Elem num : xs)) rest'
|
|
| otherwise = parse (List xs) rest
|
|
where
|
|
(cur, rest) = fromJust $ T.uncons txt
|
|
(T.decimal -> Right (num, ""), rest') = T.span isDigit txt
|