[adventofcode2018.git] / day01 / part2.hs

import qualified Data.Set as S

main = do
    contents <- getContents
    let freqs = cycle $ map toInt (lines contents)
    print $ findDouble (S.empty :: S.Set Int) 0 freqs

toInt :: String -> Int
toInt (x:xs) = if x == '+'
               then read xs :: Int
               else -(read xs :: Int)

findDouble :: S.Set Int -> Int -> [Int] -> Int
findDouble history total (x:xs)
    | S.member total history = total
    | otherwise = findDouble nextHist nextTotal xs
        where nextHist = S.insert total history
              nextTotal = total + x
Commit	Line	Data
b2f8fbc5 JK	1	import qualified Data.Set as S
	2
	3	main = do
	4	contents <- getContents
	5	let freqs = cycle $ map toInt (lines contents)
	6	print $ findDouble (S.empty :: S.Set Int) 0 freqs
	7
	8	toInt :: String -> Int
	9	toInt (x:xs) = if x == '+'
	10	then read xs :: Int
	11	else -(read xs :: Int)
	12
	13	findDouble :: S.Set Int -> Int -> [Int] -> Int
	14	findDouble history total (x:xs)
	15	\| S.member total history = total
	16	\| otherwise = findDouble nextHist nextTotal xs
	17	where nextHist = S.insert total history
	18	nextTotal = total + x