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Day 5, parts 1 & 2: Optimize `reacts` to only use one pass.

This commit is contained in:
Jesse D. McDonald 2018-12-08 00:29:03 -06:00
parent d9bce28737
commit e984a3cc10
2 changed files with 13 additions and 17 deletions
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15
Day5/Part1.hs
View File

@ -1,21 +1,18 @@
#! /usr/bin/env stack #! /usr/bin/env stack
-- stack --resolver lts-12.20 --install-ghc script -- stack --resolver lts-12.20 --install-ghc script
{-# LANGUAGE FlexibleContexts, LambdaCase #-} {-# LANGUAGE ViewPatterns #-}
module Main where module Main where
import Data.Function (fix)
import qualified Data.Char as C import qualified Data.Char as C
import qualified Data.List as L import qualified Data.List as L
main :: IO () main :: IO ()
main = interact $ show . react . takeWhile C.isAlpha main = interact $ show . length . react . takeWhile C.isAlpha
react input = react [] = []
let scan (x:y:zs) = if x `reactsWith` y then scan zs else (x : scan (y:zs)) react (x:(react -> ys))
scan zs = zs | (y:ys') <- ys, x `reactsWith` y = ys'
input' = scan input | otherwise = x:ys
result = (input', length input')
in if input' == input then result else react input'
x `reactsWith` y = (C.isUpper x && C.toLower x == y) || x `reactsWith` y = (C.isUpper x && C.toLower x == y) ||
(C.isLower x && C.toUpper x == y) (C.isLower x && C.toUpper x == y)

15
Day5/Part2.hs
View File

@ -1,6 +1,6 @@
#! /usr/bin/env stack #! /usr/bin/env stack
-- stack --resolver lts-12.20 --install-ghc script -- stack --resolver lts-12.20 --install-ghc script
{-# LANGUAGE FlexibleContexts, LambdaCase #-} {-# LANGUAGE ViewPatterns #-}
module Main where module Main where
import Data.Function (fix, on) import Data.Function (fix, on)
@ -9,16 +9,15 @@ import qualified Data.List as L
main :: IO () main :: IO ()
main = interact $ \input -> show $ L.minimumBy (compare `on` snd) $ main = interact $ \input -> show $ L.minimumBy (compare `on` snd) $
[ react $ filter (\c -> C.isAlpha c && c /= r && c /= C.toUpper r) input [ let rs = react input' in ((rs, r), length rs)
| r <- ['a'..'z'] | r <- ['a'..'z']
, let input' = [ c | c <- input, C.isAlpha c, c /= r, c /= C.toUpper r ]
] ]
react input = react [] = []
let scan (x:y:zs) = if x `reactsWith` y then scan zs else (x : scan (y:zs)) react (x:(react -> ys))
scan zs = zs | (y:ys') <- ys, x `reactsWith` y = ys'
input' = scan input | otherwise = x:ys
result = (input', length input')
in if input' == input then result else react input'
x `reactsWith` y = (C.isUpper x && C.toLower x == y) || x `reactsWith` y = (C.isUpper x && C.toLower x == y) ||
(C.isLower x && C.toUpper x == y) (C.isLower x && C.toUpper x == y)