From bc08c78977337ad3dffc5cf4110e4967eab8ce15 Mon Sep 17 00:00:00 2001
From: toastyandwarm <toby@prufrock.co.uk>
Date: Mon, 2 Dec 2024 10:21:49 +0000
Subject: [PATCH] day 2

---
 2/solution.hs | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)
 create mode 100644 2/solution.hs

diff --git a/2/solution.hs b/2/solution.hs
new file mode 100644
index 0000000..2be9d7d
--- /dev/null
+++ b/2/solution.hs
@@ -0,0 +1,47 @@
+import Data.List
+import Debug.Trace
+
+addFirst :: [[a]] -> a -> [[a]]
+addFirst [] x = [[x]]
+addFirst (y:ys) x = ([x] ++ y) : ys
+
+split :: [Char] -> [Char] -> [[Char]]
+split _ [] = []
+split delims (x:xs)
+  | elem x delims = [[]] ++ split delims xs
+  | otherwise     = addFirst (split delims xs) x
+
+splitInput :: String -> [[Int]]
+splitInput text = map (map read) $ map (filter (/="")) $ map (split [' ']) $ split ['\n'] text
+
+solve1 :: [[Int]] -> Int
+solve1 x = length $ filter (\x -> ((decreasing x) || (increasing x)) && (differences x)) x
+
+solve2 :: [[Int]] -> Int
+solve2 x = length $ filter (foldl (||) False) $ map (map (\x -> ((decreasing x) || (increasing x)) && (differences x))) $ map modifiedSets x
+
+modifiedSets :: [Int] -> [[Int]]
+modifiedSets x = map (removeElem x) ([0..length x])
+
+removeElem :: [Int] -> Int -> [Int]
+removeElem [] _ = []
+removeElem (x:xs) 0 = xs
+removeElem (x:xs) n = x : removeElem xs (n-1)
+
+increasing :: [Int] -> Bool
+increasing x = (\(x, y) -> x) $ foldl' (\(x, y) z -> (x && (y < z), z)) (True, 0) x
+
+decreasing :: [Int] -> Bool
+decreasing x = (\(x, y) -> x) $ foldr (\z (x, y) -> (x && (y < z), z)) (True, 0) x
+
+differences :: [Int] -> Bool
+differences x = (\(x, y) -> x) $ foldl (\(x, y) z -> (x && (0 < abs(y-z) && abs(y-z) < 4), z)) (True, head x-2) x
+
+main :: IO()
+main = do
+       fileinp <- readFile "input.txt"
+       let parsed = splitInput fileinp
+       let solved1 = solve1 parsed
+       let solved2 = solve2 parsed
+       print solved1
+       print solved2