From fa811780b391c3687ce1cf477515cb82b5bd345d Mon Sep 17 00:00:00 2001
From: Jan Tuomi <jans.tuomi@gmail.com>
Date: Thu, 2 Dec 2021 10:45:26 +0200
Subject: Day 02

---
 day02/main.hs | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 day02/main.hs

(limited to 'day02/main.hs')

diff --git a/day02/main.hs b/day02/main.hs
new file mode 100644
index 0000000..ac740ce
--- /dev/null
+++ b/day02/main.hs
@@ -0,0 +1,35 @@
+module Main where
+
+import Data.Foldable (Foldable (foldl'))
+import Utils
+
+toDelta :: (String, Int) -> (Int, Int)
+toDelta ("up", n) = (0, - n)
+toDelta ("down", n) = (0, n)
+toDelta ("forward", n) = (n, 0)
+toDelta x = error $ "invalid instruction: " ++ show x
+
+e1 :: [(String, Int)] -> Int
+e1 =
+  map toDelta
+    .> foldl' (\(ax, ay) (x, y) -> (ax + x, ay + y)) (0, 0)
+    .> uncurry (*)
+
+e2 :: [(String, Int)] -> Int
+e2 =
+  map toDelta
+    .> foldl' (\(ax, ay, aaim) (x, aim) -> (ax + x, ay + aaim * x, aaim + aim)) (0, 0, 0)
+    .> \(x, y, _) -> x * y
+
+main :: IO ()
+main =
+  do
+    contents <- getContents
+    let input =
+          contents
+            $> lines
+            .> map words
+            .> map (\[x, y] -> (x, read y))
+
+    e1 input $> print
+    e2 input $> print
-- 
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