From 2162be2ddeec714cdc992c2e1dfd7ab7c309fa8f Mon Sep 17 00:00:00 2001
From: Ole Morud <ole.morud@gmail.com>
Date: Sun, 1 Dec 2024 21:14:25 +0100
Subject: [PATCH] Day 1

---
 01/gold.hs   | 35 +++++++++++++++++++++++++++++++++++
 01/silver.hs | 21 +++++++++++++++++++++
 01/test.txt  |  3 +++
 3 files changed, 59 insertions(+)
 create mode 100644 01/gold.hs
 create mode 100644 01/silver.hs
 create mode 100644 01/test.txt

diff --git a/01/gold.hs b/01/gold.hs
new file mode 100644
index 0000000..27ae7d9
--- /dev/null
+++ b/01/gold.hs
@@ -0,0 +1,35 @@
+
+import Data.List -- sort
+import Data.Map (Map)
+import qualified Data.Map.Strict as Map.Strict
+import qualified Data.Map as Map
+
+mapTuple :: (a -> b) -> (a, a) -> (b, b)
+mapTuple f (a1, a2) = (f a1, f a2)
+
+countH :: Ord a => Map a Integer -> [a] -> Map a Integer
+countH m (x:xs) = countH newmap xs
+    where newmap = Map.Strict.insertWith (+) x 1 m
+countH m _ = m
+
+count :: Ord a => [a] -> Map a Integer
+count = countH Map.empty
+
+applyToSecond :: (b->c) -> (a, b) -> (a, c) 
+applyToSecond f (x, y) = (x, f y)
+
+toColumnsH :: [a] -> [a] -> [a] -> ([a], [a])
+toColumnsH ls rs (x:xs) = toColumnsH rs (ls++[x]) xs
+toColumnsH ls rs _ = (ls, rs)
+
+toColumns :: [a] -> ([a], [a])
+toColumns = toColumnsH [] []
+
+similarityH :: Integer -> Map Integer Integer -> [Integer] -> Integer
+similarityH acc m (x:xs) = similarityH (acc + x * (Map.findWithDefault 0 x m)) m xs
+similarityH acc m _ = acc
+
+similarity :: ([Integer], Map Integer Integer) -> Integer
+similarity (xs, m) = similarityH 0 m xs
+
+main = interact $ show . similarity . applyToSecond count . mapTuple sort . toColumns . map read . words
diff --git a/01/silver.hs b/01/silver.hs
new file mode 100644
index 0000000..3885336
--- /dev/null
+++ b/01/silver.hs
@@ -0,0 +1,21 @@
+
+import Data.List -- sort
+
+mapTuple :: (a -> b) -> (a, a) -> (b, b)
+mapTuple f (a1, a2) = (f a1, f a2)
+
+-- helper function for split
+splitH :: [a] -> [a] -> [a] -> ([a], [a])
+splitH ls rs (x:xs) = splitH rs (ls++[x]) xs
+splitH ls rs _ = (ls, rs)
+
+-- split: split list into two by alternating between left and right
+split :: [a] -> ([a], [a])
+split = splitH [] []
+
+-- calculates the sum of the absolute distance between two lists
+dist :: Int -> ([Int], [Int]) -> Int
+dist acc (l:ls, r:rs) = dist (acc + abs (r - l)) (ls, rs)
+dist acc _ = acc
+
+main = interact $ show . dist 0 . mapTuple sort . split . map (read :: String -> Int) . words
diff --git a/01/test.txt b/01/test.txt
new file mode 100644
index 0000000..869f967
--- /dev/null
+++ b/01/test.txt
@@ -0,0 +1,3 @@
+5 6
+3 4
+1 2