Add 2015 sources

1 files changed, 52 insertions, 0 deletions

diff --git a/2015/day11.hs b/2015/day11.hs
new file mode 100644
index 0000000..f3c05b3
--- /dev/null
+++ b/2015/day11.hs
@@ -0,0 +1,52 @@
+module Main where
+
+import Data.Char
+import Numeric
+
+pairs :: String -> [(Char,Char)]
+pairs (a:b:cs) = (a,b) : pairs (b:cs)
+pairs _ = []
+
+allEqual :: (Eq a) => [a] -> Bool
+allEqual (a:b:cs) = if a /= b then False else allEqual (b:cs)
+allEqual _ = True
+
+
+hasStraight :: String -> Bool
+hasStraight (a:b:c:ds) = (y == x + 1 && z == x + 2) || hasStraight (b:c:ds)
+    where (x,y,z) = (ord a,ord b,ord c)
+hasStraight _ = False
+
+hasForbidden :: String -> Bool
+hasForbidden [] = False
+hasForbidden (x:xs) = x /= 'i' && x /= 'o' && x /= 'l' && not (hasForbidden xs)
+
+hasTwoPairs :: String -> Bool
+hasTwoPairs s = (not.allEqual) $ filter (\(a,b) -> a == b) (pairs s)
+
+isValid :: String -> Bool
+isValid s = hasStraight s && not (hasForbidden s) && hasTwoPairs s
+
+
+show26 :: Int -> String
+show26 n = showIntAtBase 26 (\d -> chr (97 + d)) n ""
+
+read26 :: String -> Int
+read26 = fst . head . readInt 26 (\c -> let o = ord c in 97 <= o && o <= 122) (\c -> ord c - 97)
+
+pad :: Int -> Char -> String -> String
+pad n c s = if length s < n then pad n c (c:s) else s
+
+
+nextpass :: String -> String
+nextpass s = pad (length s) 'a' $ show26 $ succ $ read26 s
+
+nextvalidpass :: String -> String
+nextvalidpass = head . dropWhile (not . isValid) . iterate nextpass
+
+
+day11 :: IO ()
+day11 = do
+  print $ nextvalidpass $ nextpass $ nextvalidpass "cqjxjnds"
+
+main = day11