Hi, Note: Following code is a solution for a problem from hackerrank.com (Category: Artifical Intelligence / Single Player Games / Bot saves princess). Here is my first Haskell code! Short explanation of the problem: it's standard path finding problem, we have a matrix where 'm' denotes the bot, 'p' denotes the princess and '-' is for empty space. Sample input (grid size followed by the grid itself, where each row is separated by new line): 3 --- -m- p-- Sample output: DOWN LEFT Here is the code: module Main where import Data.List import Data.Maybe type Size = Int type Grid = [String] type Path = [Move] type Heuristic = [[Int]] type Position = (Int,Int) data Move = LEFT | RIGHT | UP | DOWN deriving Show getSize :: IO Size getSize = readLn getGrid :: Size -> IO Grid getGrid s = sequence $ replicate s getLine getHeuristic :: Size -> Position -> Heuristic getHeuristic s p = map (getHeuristic' s p) [0..s-1] getHeuristic' :: Size -> Position -> Int -> [Int] getHeuristic' s p y = map (getHeuristic'' p y) [0..s-1] getHeuristic'' :: Position -> Int -> Int -> Int getHeuristic'' (x2, y2) y1 x1 = abs (x1 - x2) + (abs (y1 - y2)) getPos :: Char -> Size -> Grid -> Position getPos c s g = (i `mod` s, i `div` s) where g' = concat g i = fromJust $ elemIndex c g' getSteps :: Size -> Heuristic -> Position -> Position -> Path getSteps s h b p | b == p = [] | otherwise = let (m,b') = getStep s h b in m : (getSteps s h b' p) getStep :: Size -> Heuristic -> Position -> (Move,Position) getStep s h b = head $ sortBy compareCost (getAvailableSteps s h b) where compareCost (_,(x1,y1)) (_,(x2,y2)) = compare (h !! y1 !! x1) (h !! y2 !! x2) getAvailableSteps :: Size -> Heuristic -> Position -> [(Move,Position)] getAvailableSteps s h (x,y) = up ++ down ++ left ++ right where up = if y > 0 then [(UP, (x, y - 1))] else [] down = if y < (s - 1) then [(DOWN, (x, y + 1))] else [] left = if x > 0 then [(LEFT, (x - 1, y))] else [] right = if x < (s - 1) then [(RIGHT, (x + 1, y))] else [] main :: IO () main = do size <- getSize grid <- getGrid size let botPos = getPos 'm' size grid princessPos = getPos 'p' size grid heuristic = getHeuristic size princessPos result = getSteps size heuristic botPos princessPos mapM_ print result Please point out all my mistakes. Emanuel