From 0305b145a762508f23c72d0eb497b04e2b7cef9e Mon Sep 17 00:00:00 2001
From: Martin Potier <martin.potier@marvid.fr>
Date: Thu, 10 Dec 2020 14:26:48 +0200
Subject: [PATCH] Part 1 done

---
 day9/main.hs | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/day9/main.hs b/day9/main.hs
index d75ea03..1fa4e84 100755
--- a/day9/main.hs
+++ b/day9/main.hs
@@ -1,20 +1,50 @@
 #! /usr/bin/env -S"ANSWER=42" nix-shell
 #! nix-shell -p ghcid
-#! nix-shell -p "haskellPackages.ghcWithPackages (p: with p; [pretty-simple])"
+#! nix-shell -p "haskellPackages.ghcWithPackages (p: with p; [pretty-simple containers])"
 #! nix-shell -i "ghcid -c 'ghci' -T main"
 
 {-# OPTIONS_GHC -Wall -Wincomplete-uni-patterns #-}
 {-# OPTIONS_GHC -Wno-unused-top-binds -Wno-unused-imports #-}
 {-# LANGUAGE OverloadedStrings #-}
 
+import Data.IntSet (IntSet)
+import Data.List (tails)
 import Debug.Trace (trace)
 import Text.Pretty.Simple
+import qualified Data.IntSet as S
+
 
 exampleData :: [Int]
 exampleData = [ 35,20,15,25,47,40,62,55,65,95,102,117,150
               , 182,127,219,299,277,309,576 ];
 
+pairSums :: [Int] -> IntSet
+pairSums xs = S.fromList $ do
+  i1 <- xs
+  i2 <- xs
+  pure (i1 + i2)
+
+isSumOfPreamble :: Int -> [Int] -> Bool
+isSumOfPreamble size xs = go tx
+  where
+    go (x:_)  = x `S.member` (pairSums preamble)
+    go ([])   = False
+    (preamble, tx) = splitAt size xs
+
+solvePart1 :: Int -> [Int] -> (Int,Bool)
+solvePart1 size message =
+  head $ dropWhile (snd) $
+  map go ( takeWhile ((> size) . length) $ tails message )
+  where
+    go xs = (head $ drop size xs,isSumOfPreamble size xs)
+
 main :: IO ()
 main = do
   putStrLn "Test"
+  print exampleData
+  print $ 1 `S.member` (pairSums [])
+  print $ pairSums exampleData
   putStrLn "Day 9 - Part 1"
+  print $ solvePart1 5 exampleData
+  input <- lines <$> readFile "day9/input"
+  print $ solvePart1 25 $ map read input