Project Eular 11 by Haskell

gistfile1.hs

import Data.List

grid :: [Integer]
grid = [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
       ,81,49,31,73,55,79,14,29,93,71,40,67,53,88,30,03,49,13,36,65
       ,52,70,95,23,04,60,11,42,69,24,68,56,01,32,56,71,37,02,36,91
       ,22,31,16,71,51,67,63,89,41,92,36,54,22,40,40,28,66,33,13,80
       ,24,47,32,60,99,03,45,02,44,75,33,53,78,36,84,20,35,17,12,50
       ,32,98,81,28,64,23,67,10,26,38,40,67,59,54,70,66,18,38,64,70
       ,67,26,20,68,02,62,12,20,95,63,94,39,63,08,40,91,66,49,94,21
       ,24,55,58,05,66,73,99,26,97,17,78,78,96,83,14,88,34,89,63,72
       ,21,36,23,09,75,00,76,44,20,45,35,14,00,61,33,97,34,31,33,95
       ,78,17,53,28,22,75,31,67,15,94,03,80,04,62,16,14,09,53,56,92
       ,16,39,05,42,96,35,31,47,55,58,88,24,00,17,54,24,36,29,85,57
       ,86,56,00,48,35,71,89,07,05,44,44,37,44,60,21,58,51,54,17,58
       ,19,80,81,68,05,94,47,69,28,73,92,13,86,52,17,77,04,89,55,40
       ,04,52,08,83,97,35,99,16,07,97,57,32,16,26,26,79,33,27,98,66
       ,88,36,68,87,57,62,20,72,03,46,33,67,46,55,12,32,63,93,53,69
       ,04,42,16,73,38,25,39,11,24,94,72,18,08,46,29,32,40,62,76,36
       ,20,69,36,41,72,30,23,88,34,62,99,69,82,67,59,85,74,04,36,16
       ,20,73,35,29,78,31,90,01,74,31,49,71,48,86,81,16,23,57,05,54
       ,01,70,54,71,83,51,54,69,16,92,33,48,61,43,52,01,89,19,67,48]

grid_max :: Integer
grid_max = 20 * 20 - 1

start_grid :: Integer -> Integer
start_grid x = last $ sort $ map go_grid $ map (\direction -> [ (grid !! (fromIntegral x)),direction,x,1]) [1..8]
-- [[[保管された値,方向,座標,回数] ..],[...] ..]

go_grid :: [Integer] -> Integer
go_grid [result_value,direct,x,time_limit]
    | (x `mod` 20 == 0 && direct == 4)||(x `mod` 20 == 19 && direct == 5) = result_value 
    | go_number < 0 || go_number > grid_max = result_value
    | time_limit == 4 = result_value
    | otherwise = go_grid [result_value * (grid !! (fromIntegral go_number)),direct,go_number,time_limit + 1]
    where
        direction
            | direct == 1 = -21
            | direct == 2 = -20
            | direct == 3 = -19
            | direct == 4 = -1
            | direct == 5 = 1
            | direct == 6 = 19
            | direct == 7 = 20
            | direct == 8 = 21
        go_number = x + direction

main = putStrLn $ show $ last $ sort $ map start_grid [0..grid_max]