Problem 12

Decompress the run-length encoded list generated in Problem 11.

rleDecode [Run 4 1, Single 2, Run 2 5, Single 2, Single 1]
    == [1, 1, 1, 1, 2, 5, 5, 2, 1]

Unit Test

import Html
import List


type RleCode a
    = Run Int a
    | Single a


rleDecode : List (RleCode a) -> List a
rleDecode list =
    -- your implementation goes here
    []


main : Html.Html a
main =
    Html.text
        <| case test of
            0 ->
                "Your implementation passed all tests."

            1 ->
                "Your implementation failed one test."

            x ->
                "Your implementation failed " ++ (toString x) ++ " tests."


test : Int
test =
    List.length
        <| List.filter ((==) False)
            [ rleDecode [ Run 4 1, Single 2, Run 2 5, Single 2, Single 1 ]
                == [ 1, 1, 1, 1, 2, 5, 5, 2, 1 ]
            , rleDecode [ Run 4 1, Single 2, Run 2 5, Single 2, Single 1 ]
                == [ 1, 1, 1, 1, 2, 5, 5, 2, 1 ]
            , rleDecode [ Run 4 "1", Single "b", Run 2 "5", Single "2", Single "a" ]
                == [ "1", "1", "1", "1", "b", "5", "5", "2", "a" ]
            ]

Hints

1. Check out List.concatMap.

Solutions

Solutions