Hi, I'm the original author of this Kata (Ruby version). Author of the haskell version didn't understand this Kata properly, and indeed added a DFS version instead of BFS.

I have learned haskell to fix this. I added a BFS solution and a correct buildTree (thanks to @nickie for providing one). Please take a look again.

Thanks,
Karol

This has been reported several times, but the author isn't active anymore. See the issues by @muesli4, @karoyakani, @knotman90, @Thom, @lisphacker and @pcapriotti.

manhattanDistance( [1, 1], [1, 1] ) => returns 0

is the example provided for JS users.
(The description wasn't modified for Haskell)