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| -rw-r--r-- | challenge-089/ulrich-rieke/haskell/ch-2.hs | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/challenge-089/ulrich-rieke/haskell/ch-2.hs b/challenge-089/ulrich-rieke/haskell/ch-2.hs new file mode 100644 index 0000000000..47ae1f3d45 --- /dev/null +++ b/challenge-089/ulrich-rieke/haskell/ch-2.hs @@ -0,0 +1,45 @@ +module Challenge089_2 + where +import Data.List ( (!!) ) +import Data.List.Split ( chunksOf ) + +count :: Eq a => a -> [a] -> Int +count c [] = 0 +count d (x:xs) + |d == x = 1 + count d xs + |otherwise = count d xs + +--find all lists that fulfill the sum conditions, in a list comprehension +possibleLists :: [[Int]] +possibleLists = [[a , b , c , d , e , f , g , h , i] | a <- [1 .. 9] , +b <- [1 .. 9], c <- [1 .. 9] , d <- [1 .. 9], e <- [1 .. 9] , f <- [1 .. 9], +g <- [1 .. 9], h <- [1 .. 9], i <- [1 .. 9] , +a + b + c == 15, d + e + f == 15 , g + h + i == 15, +a + d + g == 15 , b + e + h == 15 , c + f + i == 15 , a + e + i == 15 , +c + e + g == 15] + +--in all possible lists find those where every number occurs only once +validLists :: [[Int]] +validLists = filter myCondition possibleLists + where + myCondition :: [Int] -> Bool + myCondition sublist = all ( 1 == ) $ map (\n -> count n sublist ) + sublist + +--convert a row of 3 numbers into a string +convertRow :: [Int] -> String +convertRow row = "[ " ++ (show $ row !! 0 ) ++ " " ++ ( show $ row !! 1 ) +++ " " ++ ( show $ row !! 2 ) ++ " ]" + +--convert three rows of 3 numbers each into a "magic square" +--first, convert each row to a string, and then print that string +--after the 3rd row of the square add an empty line +printSquare :: [Int] -> IO ( ) +printSquare magic = do + let rows = map convertRow $ chunksOf 3 magic + mapM_ putStrLn rows + putStrLn " " + +main :: IO ( ) +main = do + mapM_ printSquare validLists |