From 56f6951415a1be410da430096a20603b50bc9272 Mon Sep 17 00:00:00 2001
From: Amneesh Singh <natto@weirdnatto.in>
Date: Sun, 17 Dec 2023 21:42:23 +0530
Subject: [PATCH] day 11

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>
---
 day11.hs | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 day11.hs

diff --git a/day11.hs b/day11.hs
new file mode 100644
index 0000000..7cf8e5d
--- /dev/null
+++ b/day11.hs
@@ -0,0 +1,31 @@
+import Data.List (tails)
+
+type Coord = (Int, Int)
+
+-- slow but dont care
+main :: IO ()
+main = do
+  input <- lines <$> readFile "day11.in"
+
+  let galaxies = [(x, y) | (row, x) <- zip input [0 ..], ('#', y) <- zip row [0 ..]]
+
+  let emptyRows = [r | r <- [0 .. length input], r `notElem` map fst galaxies]
+  let emptyCols = [c | c <- [0 .. length $ head input], c `notElem` map snd galaxies]
+
+  let galaxyPairs = [(x, y) | (x : xs) <- tails galaxies, y <- xs]
+
+  putStr "Q1: "
+  print . sum $ map (uncurry $ distance emptyRows emptyCols 2) galaxyPairs
+
+  putStr "Q2: "
+  print . sum $ map (uncurry $ distance emptyRows emptyCols 1000000) galaxyPairs
+
+distance :: [Int] -> [Int] -> Int -> Coord -> Coord -> Int
+distance rs cs f (x1, y1) (x2, y2) =
+  abs (x1 - x2)
+    + abs (y1 - y2)
+    + (f - 1) * length (filter (between x1 x2) rs)
+    + (f - 1) * length (filter (between y1 y2) cs)
+
+between :: Int -> Int -> Int -> Bool
+between a b x = x > min a b && x < max a b