From 66a0927e1c274f32f4096f82587160dd7af8def6 Mon Sep 17 00:00:00 2001
From: Neil Smith <neil.git@njae.me.uk>
Date: Sun, 2 Dec 2018 11:57:39 +0000
Subject: [PATCH] Tidying day 2

---
 src/advent02/advent02.hs | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/src/advent02/advent02.hs b/src/advent02/advent02.hs
index f2408de..c2bd908 100644
--- a/src/advent02/advent02.hs
+++ b/src/advent02/advent02.hs
@@ -1,6 +1,5 @@
 import Data.List
 
-
 main :: IO ()
 main = do 
         text <- readFile "data/advent02.txt"
@@ -17,18 +16,12 @@ letterCounts = map length . group . sort
 
 addCounts :: (Int, Int) -> [Int] -> (Int, Int)
 addCounts (twos, threes) counts = (twos', threes')
-    where twos'   = if has2 counts then twos + 1   else twos
-          threes' = if has3 counts then threes + 1 else threes
-
-has2 = elem 2
-has3 = elem 3
+    where twos'   = if 2 `elem` counts then twos + 1   else twos
+          threes' = if 3 `elem` counts then threes + 1 else threes
 
-part2 ids = uncurry sameChars closeIds
-    where closeIds = head $ filter (\ab -> uncurry differenceCount ab == 1) [(a, b) | a <- ids, b <- ids]
+part2 ids = uncurry intersect closeIds
+    where closeIds = head $ filter (\ab -> uncurry differenceCount ab == 1) 
+                        [(a, b) | a:rest <- tails ids, b <- rest]
 
 differenceCount :: String -> String -> Int
 differenceCount this that = length $ filter (\(a, b) -> a /= b) $ zip this that
-
-sameChars :: String -> String -> String
-sameChars this that = map fst $ filter (\(a, b) -> a == b) $ zip this that
-
-- 
2.34.1