From 36b7ae3736c9ab52da7994bde0cb3ed657efc721 Mon Sep 17 00:00:00 2001
From: Yuchen Pei <me@ypei.me>
Date: Thu, 28 Dec 2017 23:06:19 +0100
Subject: All done!

---
 Puzzle24.hs | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
 create mode 100644 Puzzle24.hs

(limited to 'Puzzle24.hs')

diff --git a/Puzzle24.hs b/Puzzle24.hs
new file mode 100644
index 0000000..639f4a3
--- /dev/null
+++ b/Puzzle24.hs
@@ -0,0 +1,26 @@
+-- Acknowledgements:
+-- https://www.reddit.com/r/adventofcode/comments/7lte5z/2017_day_24_solutions/drs1eml/
+-- https://stackoverflow.com/a/4708372/4063224
+import Data.List (delete, concatMap)
+import Data.List.Split (splitOn)
+
+extBridge :: [Int] -> [[Int]] -> [[Int]]
+extBridge xs ys
+  | null zs = [xs]
+  | otherwise = concatMap f zs
+    where x = head xs
+          zs = filter (elem x) ys
+          f [y, z] = extBridge (if y == x then (z:y:xs) else (y:z:xs)) (delete [y, z] ys)
+
+parseInput :: [Char] -> [[Int]]
+parseInput xs = (fmap read . splitOn "/") <$> splitOn "\n" xs
+
+solve1 :: [Char] -> Int
+solve1 = maximum . fmap sum . (extBridge [0]) . parseInput
+
+solve2 :: [Char] -> Int
+solve2 = snd . maximum . fmap (\xs -> (length xs, sum xs)) . (extBridge [0]) . parseInput
+
+input0 = "0/2\n2/2\n2/3\n3/4\n3/5\n0/1\n10/1\n9/10"
+
+input = "50/41\n19/43\n17/50\n32/32\n22/44\n9/39\n49/49\n50/39\n49/10\n37/28\n33/44\n14/14\n14/40\n8/40\n10/25\n38/26\n23/6\n4/16\n49/25\n6/39\n0/50\n19/36\n37/37\n42/26\n17/0\n24/4\n0/36\n6/9\n41/3\n13/3\n49/21\n19/34\n16/46\n22/33\n11/6\n22/26\n16/40\n27/21\n31/46\n13/2\n24/7\n37/45\n49/2\n32/11\n3/10\n32/49\n36/21\n47/47\n43/43\n27/19\n14/22\n13/43\n29/0\n33/36\n2/6"
-- 
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