Hi. My plan is just add some *unusable* data to make diagonal grid normally. Here this is. p011_input = input ++ (transpose input) ++ diagInput ++ diagInputT where diagInput = p011_toDiag input diagInputT = p011_toDiag . (map reverse) $ input input = [ [08,02,22,97,38,15,00,40,00,75,04,05,07,78,52,12,50,77,91,08], [49,49,99,40,17,81,18,57,60,87,17,40,98,43,69,48,04,56,62,00], ... , [01,70,54,71,83,51,54,69,16,92,33,48,61,43,52,01,89,19,67,48] ] p011_toDiag = (map remove) . transpose . (map append) . addIndex where addIndex = zip [0..] append (n,y) = replicate n (-1) ++ y ++ replicate (19-n) (-1) remove = filter (-1/=) p011_toGroups x = case x of (a:b:c:d:xs) -> [a,b,c,d] : p011_toGroups (b:c:d:xs) _ -> [] p011_solve = putStrLn . show $ (foldl1 max) . (map product) . concat . (map p011_toGroups) $ p011_input ------------------ L.Guo 2007-08-17 ------------------------------------------------------------- From: Ronald Guida At: 2007-07-20 11:39:50 Subject: [Haskell-cafe] Hints for Euler Problem 11 To handle the diagonals, my plan is to try to extract each diagonal as a list of elements and put all the diagonals into a list; then I can use maxHorizontal. I came up with this function to try to extract the main diagonal.
getDiag :: [[a]] -> [a] getDiag = map (head . head) . iterate (tail . map tail)
The problem is, this function doesn't work unless I have an infinite grid.