Done day 10

[advent-of-code-20.git] / advent10 / src / advent10.hs

diff --git a/advent10/src/advent10.hs b/advent10/src/advent10.hs
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+++ b/advent10/src/advent10.hs
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+-- import Debug.Trace
+
+import qualified Data.Map as M
+-- import qualified Data.Set as S
+import Data.List
+
+main :: IO ()
+main = 
+    do  
+        numStrs <- readFile "data/advent10.txt"
+        let nums = map (read @Int) $ lines numStrs
+        let device = 3 + maximum nums
+        let sortedNums = sort (0:device:nums)
+        print $ part1 sortedNums
+        print $ part2 sortedNums
+
+part1 :: [Int] -> Int
+part1 nums = jolt1s * jolt3s
+    where jolt1s = joltNs 1 nums
+          jolt3s = joltNs 3 nums
+
+joltNs d ns = length $ filter diff $ zip ns (tail ns)
+    where diff (a, b) = (b - a) == d
+
+part2 :: [Int] -> Int
+part2 nums = snd $ M.findMax $ foldl includeAdapter (M.singleton 0 1) $ tail nums
+
+includeAdapter arrangements adapter = M.insert adapter earlierCount arrangements
+    where 
+        earlierArrangements = M.filterWithKey (\k _ -> (adapter - k) <= 3) arrangements
+        earlierCount = M.foldl (+) 0 earlierArrangements