Initial commit

2017/05/day5.hs

@@ -0,0 +1,36 @@
+#!/usr/bin/env stack
+-- stack --resolver lts-9.14 script
+
+jump :: Int -> [Int] -> [Int] -> Maybe ([Int], [Int])
+jump n back front =
+  if n == 0 then
+    Just (back, front)
+  else if n > 0 then
+    case front of
+      [] -> Nothing
+      x:xs -> jump (n-1) (x:back) xs
+  else
+    case back of
+      [] -> Nothing
+      x:xs -> jump (n+1) xs (x:front)
+
+countJumps :: Int -> [Int] -> [Int] -> Int
+countJumps count back [] = count
+countJumps count back (x:xs) =
+  case jump x back ((x+1):xs) of
+    Nothing -> count + 1
+    Just (back', front') -> countJumps (count+1) back' front'
+
+countJumps2 :: Int -> [Int] -> [Int] -> Int
+countJumps2 count back [] = count
+countJumps2 count back (x:xs) =
+  case jump x back (newx:xs) of
+    Nothing -> count + 1
+    Just (back', front') -> countJumps2 (count+1) back' front'
+  where newx = if x >= 3 then x-1 else x+1
+
+
+main :: IO ()
+main = do
+  front <- map read <$> lines <$> getContents
+  putStrLn . show $ countJumps2 0 [] front