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Revision: 49755
at July 29, 2011 08:06 by rtperson


Updated Code
data EncodedElement a = Multiple Int a | Single a
    deriving Show

encodeModified :: (Eq a) => [a] -> [EncodedElement a]    
encodeModified = map (\x -> if (length x > 1) 
                              then Multiple (length x) (head x) 
                              else Single (head x)) . group


decodeModified :: [EncodedElement a] -> [a]
decodeModified = concatMap decode
    where 
        decode (Multiple n c) = replicate n c
        decode (Single c)     = c : []

Revision: 49754
at July 29, 2011 08:03 by rtperson


Initial Code
data EncodedElement a = Multiple Int a | Single a
    deriving Show

encodeModified :: (Eq a) => [a] -> [EncodedElement a]    
encodeModified = map (\x -> if (length x > 1) 
                              then Multiple (length x) (head x) 
                              else Single (head x)) . group
                              
isMultiple :: EncodedElement a -> Bool
isMultiple x = case x of
                Multiple _ _ -> True
                Single   _   -> False


decodeModified :: [EncodedElement a] -> [a]
decodeModified = concatMap decode
    where 
        decode (Multiple n c) = replicate n c
        decode (Single c)     = c : []

Initial URL
http://www.haskell.org/haskellwiki/99_questions/11_to_20

Initial Description
problem 11, modified run-length encoding
========================================
If an element has no duplicates, mark it as such. 

Example:

    encodeModified "aaaabccaadeeee"

    [Multiple 4 'a',Single 'b',Multiple 2 'c',
        Multiple 2 'a',Single 'd',Multiple 4 'e']

problem 12, Decode a run-length encoded list. 
=============================================
Given a run-length code list generated as specified in problem 11. Construct its uncompressed version. 

Example:

    decodeModified 
       [Multiple 4 'a',Single 'b',Multiple 2 'c',
        Multiple 2 'a',Single 'd',Multiple 4 'e']

    "aaaabccaadeeee"

Initial Title
Haskell 99 Problems - Solutions to 11 and 12

Initial Tags


Initial Language
Haskell