From edd8e1fa47c6895b28bbe61ab786ab6dc30471cd Mon Sep 17 00:00:00 2001
From: Akshay <nerdy@peppe.rs>
Date: Fri, 11 Dec 2020 10:07:13 +0530
Subject: add day10

---
 execs/Day10.hs | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 execs/Day10.hs

(limited to 'execs')

diff --git a/execs/Day10.hs b/execs/Day10.hs
new file mode 100644
index 0000000..c42a550
--- /dev/null
+++ b/execs/Day10.hs
@@ -0,0 +1,29 @@
+
+module Main where
+
+import Utils
+import Data.List (sort)
+import Control.Monad
+import Control.Monad.Memo
+
+parseLine :: String -> Int
+parseLine = read
+
+diffs :: [Int] -> Int
+diffs s = product $ ($ q s) <$> [howMany (==1), howMany (==3)]
+    where q = zipWith subtract `ap` tail
+
+combos top s = startEvalMemo $ go 0
+    where go c
+            | c == top = return 1
+            | otherwise = do
+                let cs = filter (`elem` s) $ map (+c) [1,2,3]
+                sum <$> mapM (memo go) cs
+
+main :: IO ()
+main = do
+    n <- map parseLine . lines <$> readFile "input/10"
+    let top = maximum n + 3
+        ls = sort (0:top:n)
+    print $ diffs ls
+    print $ combos top ls
-- 
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