From 9d1ecddf7b8379f440648dd2d25cac1017d57c9d Mon Sep 17 00:00:00 2001
From: Daniele Fucini <dfucini@gmail.com>
Date: Mon, 2 Dec 2024 18:29:31 +0100
Subject: [PATCH] Day 2

---
 Day2/puzzle1.hs | 14 ++++++++++++++
 Day2/puzzle2.hs | 19 +++++++++++++++++++
 2 files changed, 33 insertions(+)
 create mode 100644 Day2/puzzle1.hs
 create mode 100644 Day2/puzzle2.hs

diff --git a/Day2/puzzle1.hs b/Day2/puzzle1.hs
new file mode 100644
index 0000000..751737f
--- /dev/null
+++ b/Day2/puzzle1.hs
@@ -0,0 +1,14 @@
+import Data.List (sort)
+import System.IO
+
+isSafe :: [Int] -> Bool
+isSafe xs = (isAscending xs || isDescending xs) && maximum distances <= 3 && minimum distances >= 1
+            where isAscending xs = xs == sort xs
+                  isDescending xs = xs == reverse (sort xs)
+                  distances = map abs $ zipWith (-) xs (tail xs)
+
+main = do
+    contents <- lines <$> readFile "day2.txt"
+    let reports = map read . words <$> contents
+        safeCount = length $ filter isSafe reports
+    print safeCount
diff --git a/Day2/puzzle2.hs b/Day2/puzzle2.hs
new file mode 100644
index 0000000..f595599
--- /dev/null
+++ b/Day2/puzzle2.hs
@@ -0,0 +1,19 @@
+import Data.List (sort, inits, tails)
+import System.IO
+
+isSafe :: [Int] -> Bool
+isSafe xs = (isAscending xs || isDescending xs) && maximum distances <= 3 && minimum distances >= 1
+            where isAscending xs = xs == sort xs
+                  isDescending xs = xs == reverse (sort xs)
+                  distances = map abs $ zipWith (-) xs (tail xs)
+
+removeLevel :: [Int] -> [[Int]]
+removeLevel xs = zipWith (++) ys zs
+            where ys = map init $ tail (inits xs)
+                  zs = map tail $ init (tails xs)
+
+main = do
+    contents <- lines <$> readFile "day2.txt"
+    let reports = map read . words <$> contents
+        safeCount = length . filter (any isSafe) $ map removeLevel reports
+    print safeCount