Listing the paths to leaves in a tree

Question

I\'m trying to write a function that finds all of the paths to the leaves in a tree. For example, given a tree that looks like this:

           1
         /  \\
         


        

Answer 1

just a simple function:

listtree :: [a] -> Tree a -> [[a]]
listtree l (Node a []) = [l++[a]]
listtree l (Node a forest) = concatMap (listtree (l++[a])) forest

use a list to record path from root to current node, and append current node's label to the path, then recursively map listtree to each subnode.

listtree [] (Node 1 [(Node 2 [(Node 3 []), (Node 4 [])]), (Node 5 [(Node 6 [])])]))

yield the desired result [[1,2,3],[1,2,4],[1,5,6]]