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[hs] Solve 2020_10

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Joscha 2020-12-10 12:08:13 +00:00
parent f642872ea1
commit 8233376b4c
2 changed files with 35 additions and 0 deletions
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2
hs/src/Aoc/Y2020.hs
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@ -12,6 +12,7 @@ import qualified Aoc.Y2020.D06 as D06
import qualified Aoc.Y2020.D07 as D07
import qualified Aoc.Y2020.D08 as D08
import qualified Aoc.Y2020.D09 as D09
import qualified Aoc.Y2020.D10 as D10
year :: Year
year = Year 2020
@ -24,4 +25,5 @@ year = Year 2020
, ( 7, D07.day)
, ( 8, D08.day)
, ( 9, D09.day)
, (10, D10.day)
]

33
hs/src/Aoc/Y2020/D10.hs Normal file
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@ -0,0 +1,33 @@
module Aoc.Y2020.D10
( day
) where
import Data.List
import Aoc.Day
import Aoc.Parse
parser :: Parser [Integer]
parser = manyLines decimal
possibilities :: Integer -> Integer -> Integer -> [Integer] -> Integer
possibilities _ _ c [] = c
possibilities a b c (1:xs) = possibilities b c (a + b + c) [x - 1 | x <- xs]
possibilities _ b c (2:xs) = possibilities c 0 (b + c) [x - 2 | x <- xs]
possibilities _ _ c (3:xs) = possibilities 0 0 c [x - 3 | x <- xs]
possibilities _ _ _ (_:_) = 0
solver :: [Integer] -> IO ()
solver nums = do
let snums = sort nums ++ [maximum nums + 3]
putStrLn ">> Part 1"
let diffs = zipWith (-) snums (0 : snums)
print $ length (filter (==1) diffs) * length (filter (==3) diffs)
putStrLn ""
putStrLn ">> Part 2"
print $ possibilities 0 0 1 snums
day :: Day
day = dayParse parser solver