From f5eb3e1a98d7ec0aea08bc640ec341178d4750e6 Mon Sep 17 00:00:00 2001
From: Julien Dessaux
Date: Mon, 20 Mar 2023 00:35:17 +0100
Subject: 2020-10 in haskell

---
 2020/10-Adapter_Array/first.hs | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 2020/10-Adapter_Array/first.hs

(limited to '2020/10-Adapter_Array/first.hs')

diff --git a/2020/10-Adapter_Array/first.hs b/2020/10-Adapter_Array/first.hs
new file mode 100644
index 0000000..0157a3b
--- /dev/null
+++ b/2020/10-Adapter_Array/first.hs
@@ -0,0 +1,31 @@
+module Main (main) where
+import Control.Monad (when)
+import Data.List (foldl', sort)
+import System.Exit (die)
+
+exampleExpectedOutput = 35
+exampleExpectedOutput2 = 220
+
+parseInput :: String -> IO [Int]
+parseInput filename = do
+  input <- readFile filename
+  return $ map read $ lines input
+
+compute :: [Int] -> Int
+compute jolts = result $ foldl' compute' (0, 0, 0) $ sort jolts
+  where
+    compute' (prev, ones, threes) jolt
+      | jolt - prev == 1 = (jolt, ones + 1, threes)
+      | jolt - prev == 3 = (jolt, ones, threes + 1)
+    result (_, ones, threes) = ones * (threes + 1)
+
+main :: IO ()
+main = do
+  example <- parseInput "example"
+  let exampleOutput = compute example
+  when  (exampleOutput /= exampleExpectedOutput)  (die $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput)
+  example2 <- parseInput "example2"
+  let exampleOutput2 = compute example2
+  when  (exampleOutput2 /= exampleExpectedOutput2)  (die $ "example2 failed: got " ++ show exampleOutput2 ++ " instead of " ++ show exampleExpectedOutput2)
+  input <- parseInput "input"
+  print $ compute input
-- 
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