99 Elm Problems/Problem 11/Solutions

Solution 1: Recursive version

runLengthEncode list =
    case list of
        [] -> []
        [ x ] -> [ Single x ]
        x :: xs ->
            case runLengthEncode xs of
                [] -> []
                Single x' :: xs' ->
                    if x' == x then
                        Multiple 2 x' :: xs'
                    else
                        Single x :: Single x' :: xs'
                Multiple n x' :: xs' ->
                    if x' == x then
                        Multiple (n + 1) x' :: xs'
                    else
                        Single x :: Multiple n x' :: xs'

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