Problem 61b

Extract the values of the leaves of a binary tree into a list.

Example

tree = Tree 1 (Tree 2 Empty (Tree 4 Empty Empty))
                 (Tree 2 Empty Empty)

getLeaves aTree == [4, 2]

Unit Test

import Html
import List


type Tree a
    = Empty
    | Node a (Tree a) (Tree a)


getLeaves : Tree comparable -> List comparable
getLeaves tree =
    -- your implementation here
    []

main =
    Html.text
        (if (test) then
            "Your implementation passed all tests."
         else
            "Your implementation failed at least one test."
        )


test : Bool
test =
    List.all ((==) True)
        [ getLeaves Empty == []
        , getLeaves (Node 1 Empty Empty) == [1]
        , List.sort (getLeaves (Node 1 (Node 2 Empty Empty) Empty)) == [2]
        , List.sort (getLeaves (Node 1 (Node 2 Empty Empty) (Node 0 Empty Empty))) 
            == [0, 2]
        , List.sort (getLeaves (Node 1 (Node 2 Empty Empty) (Node 0 Empty Empty)))
            == [0, 2]
        , List.sort (getLeaves (Node "A" (Node "B" Empty Empty) (Node "C" Empty Empty)))
            == ["B", "C"]
        ]

Hints

1. You don't need no stinking hints!

Solutions

Solutions