From b1e4728107e7dcc79faf83639887d894a24d89f0 Mon Sep 17 00:00:00 2001
From: Daniele Fucini <dfucini@gmail.com>
Date: Mon, 16 Dec 2024 19:32:18 +0100
Subject: [PATCH] Day 14, Part 2

---
 adventofcode2024.cabal |  1 +
 src/Day14/Puzzle2.hs   | 42 ++++++++++++++++++++++++++++++++++++++++++
 src/Main.hs            |  2 ++
 3 files changed, 45 insertions(+)
 create mode 100644 src/Day14/Puzzle2.hs

diff --git a/adventofcode2024.cabal b/adventofcode2024.cabal
index 5707eaa..5db34e5 100644
--- a/adventofcode2024.cabal
+++ b/adventofcode2024.cabal
@@ -58,4 +58,5 @@ executable adventofcode2024
     Day13.Puzzle1
     Day13.Puzzle2
     Day14.Puzzle1
+    Day14.Puzzle2
     Day15.Puzzle1
diff --git a/src/Day14/Puzzle2.hs b/src/Day14/Puzzle2.hs
new file mode 100644
index 0000000..52b0394
--- /dev/null
+++ b/src/Day14/Puzzle2.hs
@@ -0,0 +1,42 @@
+{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
+
+module Day14.Puzzle2 (day14_2) where
+
+import Data.Char (isDigit)
+import Data.List (nub)
+import Data.List.Split (splitOn)
+
+type Position = (Int, Int)
+
+type Velocity = (Int, Int)
+
+type Robot = (Position, Velocity)
+
+readRobot :: String -> Robot
+readRobot s =
+  let [ps, vs] = splitOn " " s
+      [px, py] = map read . splitOn "," $ filter (\x -> isDigit x || x == ',' || x == '-') ps
+      [vx, vy] = map read . splitOn "," $ filter (\x -> isDigit x || x == ',' || x == '-') vs
+   in ((px, py), (vx, vy))
+
+moveRobot :: Robot -> Robot
+moveRobot r =
+  let (px, py) = fst r
+      (vx, vy) = snd r
+   in (((px + vx) `mod` 101, (py + vy) `mod` 103), (vx, vy))
+
+findChristmasTree :: Int -> [Robot] -> Int
+findChristmasTree n rs =
+  let rs' = map moveRobot rs
+      positions = map fst rs'
+   in if positions == nub positions
+        then n
+        else findChristmasTree (n + 1) rs'
+
+day14_2 :: IO ()
+day14_2 = do
+  contents <- lines <$> readFile "input/day14.txt"
+  let robots = map readRobot contents
+  putStrLn $
+    "Day 14, Puzzle 2 solution: "
+      ++ show (findChristmasTree 1 robots)
diff --git a/src/Main.hs b/src/Main.hs
index df203cb..0a325b1 100644
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -25,6 +25,7 @@ import Day12.Puzzle1
 import Day13.Puzzle1
 import Day13.Puzzle2
 import Day14.Puzzle1
+import Day14.Puzzle2
 import Day15.Puzzle1
 import System.Environment (getArgs)
 
@@ -57,5 +58,6 @@ main = do
     "13" : "1" : _ -> day13_1
     "13" : "2" : _ -> day13_2
     "14" : "1" : _ -> day14_1
+    "14" : "2" : _ -> day14_2
     "15" : "1" : _ -> day15_1
     _ -> error "Not implemented"