Day 23, Part 1

src/Day23.hs

@@ -0,0 +1,40 @@
+module Day23 (day23_1) where
+
+import Control.Monad
+import Data.Containers.ListUtils (nubOrd)
+import Data.List (nub, sort)
+import Data.List.Split (splitOn)
+
+startsWithT :: String -> Bool
+startsWithT [] = False
+startsWithT (x : _)
+  | x == 't' = True
+  | otherwise = False
+
+getConns3 :: [[String]] -> [[String]]
+getConns3 connections = do
+  conn1 <- connections
+  conn2 <- connections
+
+  guard $
+    conn1 /= conn2
+      && length (nub (conn1 ++ conn2)) == 3
+      && any startsWithT (conn1 ++ conn2)
+
+  conn3 <- connections
+
+  guard $
+    conn1 /= conn3
+      && conn2 /= conn3
+      && length (nub (conn1 ++ conn2 ++ conn3)) == 3
+      && any startsWithT (conn1 ++ conn2 ++ conn3)
+
+  return . nub $ conn1 ++ conn2 ++ conn3
+
+day23_1 :: IO ()
+day23_1 = do
+  contents <- lines <$> readFile "input/day23.txt"
+  let connections = map (splitOn "-") contents
+  putStrLn $
+    "Day 23, Puzzle 1 solution: "
+      ++ show (length . nubOrd . map sort $ getConns3 connections)