# 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) == 
, List.sort (getLeaves (Node 1 (Node 2 Empty Empty) Empty)) == 
, 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