- Added Haskell solutions by Ulrich Rieke.

2 files changed, 71 insertions, 0 deletions

diff --git a/challenge-077/ulrich-rieke/haskell/ch-1.hs b/challenge-077/ulrich-rieke/haskell/ch-1.hs
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+++ b/challenge-077/ulrich-rieke/haskell/ch-1.hs
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+module Challenge077
+  where
+import Data.List ( nub, subsequences , intercalate)
+
+fibonacci :: Int -> Int
+fibonacci 0 = 0
+fibonacci 1 = 1
+fibonacci n = fibonacci ( n - 2 ) + fibonacci ( n - 1 )
+
+findList :: Int -> [ Int ]
+findList n = nub $ takeWhile ( < n ) $ map fibonacci [1..n]
+
+convert :: [Int] -> String
+convert list = (intercalate " + " $ map show list) ++ " = " ++ ( show $
+sum list )
+
+solution :: Int -> [String]
+solution n = map convert $ filter (( n == ) . sum ) $ subsequences
+$ findList n
diff --git a/challenge-077/ulrich-rieke/haskell/ch-2.hs b/challenge-077/ulrich-rieke/haskell/ch-2.hs
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+++ b/challenge-077/ulrich-rieke/haskell/ch-2.hs
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+module Challenge077_2
+  where
+import Control.Applicative
+import Data.List ( (!!) , (\\) , findIndices )
+
+--given a row or column index in the array, which is the allowable range
+--of neighbouring rows or colums ?
+findRange :: (Int , Int ) -> Int -> [Int]
+findRange ( lowerLimit , upperLimit ) value
+  |value == lowerLimit = [value , value + 1]
+  |value > lowerLimit && value < upperLimit = [value - 1 , value , value
+    + 1 ]
+  |value == upperLimit = [ value - 1 , value ]
+  |otherwise = []
+
+--which are the indexes of neighbours to a 'x' in the array
+--look at the possible ranges of rows and columns and subtract from that
+--the index of the x
+findNeighbours :: [String] -> Int -> Int -> [(Int , Int)]
+findNeighbours array row column = ((,) <$> (findRange (0 , length array - 1)
+row) <*> ( findRange (0 , (length $ head array) - 1 ) column )) \\
+  [(row , column)]
+
+findChar :: [String] -> Int -> Int -> Char
+findChar array row column = ( array !! row ) !! column
+
+--find the x'es in every row
+find_x_Indices :: [String] -> [[Int]]
+find_x_Indices array = map (\row -> findIndices ('x' == ) row ) array
+
+--find the neighbouring indices in every line
+findAllNeighbourIndices :: [String] -> [[Int]] -> [[(Int , Int)]]
+findAllNeighbourIndices array xindices = concat $ map (\p -> map(\i ->
+findNeighbours array ( fst p ) i ) (snd p) ) $ zip [0, 1 ..] xindices
+
+--find neighbouring strings
+findStrings :: [String] -> [[(Int , Int)]] -> [String]
+findStrings array foundIndices = map (\list -> map (\p -> findChar
+array ( fst p ) ( snd p ) ) list ) foundIndices
+
+
+solution :: [String] -> Int
+solution array = length $ filter condition allNeighbourStrings
+  where
+      allXIndices :: [[Int ]]
+      allXIndices = find_x_Indices array
+      allNeighbourIndices :: [[(Int, Int)]]
+      allNeighbourIndices = findAllNeighbourIndices array allXIndices
+      allNeighbourStrings :: [String]
+      allNeighbourStrings = findStrings array allNeighbourIndices
+      condition :: String -> Bool
+      condition s = all ('o' == ) s