From 010cf614a510a83e89d4a610dee994f6e25be72e Mon Sep 17 00:00:00 2001
From: Xavier Morel <xavier.morel@cybelangel.com>
Date: Thu, 10 Dec 2020 18:06:35 +0100
Subject: [PATCH] Add 2015 day 11

---
 haskellAoC/inputs/2015/11     |  1 +
 haskellAoC/src/Y2015/Day11.hs | 35 +++++++++++++++++++++++++++++++++++
 haskellAoC/src/Y2015/Days.hs  |  2 ++
 3 files changed, 38 insertions(+)
 create mode 100644 haskellAoC/inputs/2015/11
 create mode 100644 haskellAoC/src/Y2015/Day11.hs

diff --git a/haskellAoC/inputs/2015/11 b/haskellAoC/inputs/2015/11
new file mode 100644
index 0000000..cdc0b85
--- /dev/null
+++ b/haskellAoC/inputs/2015/11
@@ -0,0 +1 @@
+cqjxjnds
\ No newline at end of file
diff --git a/haskellAoC/src/Y2015/Day11.hs b/haskellAoC/src/Y2015/Day11.hs
new file mode 100644
index 0000000..732e0ef
--- /dev/null
+++ b/haskellAoC/src/Y2015/Day11.hs
@@ -0,0 +1,35 @@
+module Y2015.Day11 (y15day11) where
+
+import Data.Char
+import Data.List
+
+allTrue :: [(a -> Bool)] -> a -> Bool
+allTrue predicates entry = all (== True) $ map ($ entry) predicates
+
+rowOfThree :: String -> Bool
+rowOfThree (x1:x2:x3:xs)
+  | c3 == (c2 + 1) && c2 == (c1 + 1) = True
+  | otherwise = rowOfThree (x2:x3:xs)
+  where c1 = ord x1
+        c2 = ord x2
+        c3 = ord x3
+rowOfThree _ = False
+
+-- Do we accept triples as 1 pair ?
+twoPairs :: String -> Bool
+twoPairs s = (>= 2) . length $ filter (== 2) $ map length $ group s
+
+isValid :: String -> Bool
+isValid s = allTrue [validChars, length8, rowOfThree, twoPairs] s
+  where validChars = all (\c -> isLower c && (c `notElem` "iol"))
+        length8 = (== 8) . length
+
+nextSequence :: String -> String
+nextSequence s = reverse $ nextSequence' $ reverse $ s
+  where nextSequence' ('z':cs) = 'a':nextSequence' cs
+        nextSequence' (c:cs) = ((chr . (+1) . ord) $ c) : cs
+        nextSequence' [] = []
+
+y15day11 :: [String] -> (String, String)
+y15day11 (input:_) = (part1, part2)
+  where [part1, part2] = take 2 $ filter isValid $ iterate nextSequence input
diff --git a/haskellAoC/src/Y2015/Days.hs b/haskellAoC/src/Y2015/Days.hs
index d5783af..2a44898 100644
--- a/haskellAoC/src/Y2015/Days.hs
+++ b/haskellAoC/src/Y2015/Days.hs
@@ -10,6 +10,7 @@ import Y2015.Day07
 import Y2015.Day08
 import Y2015.Day09
 import Y2015.Day10
+import Y2015.Day11
 
 year2015 :: String -> [String] -> (String, String)
 year2015 "01" = y15day01
@@ -22,3 +23,4 @@ year2015 "07" = y15day07
 year2015 "08" = y15day08
 year2015 "09" = y15day09
 year2015 "10" = y15day10
+year2015 "11" = y15day11