tree - How to list paths through DAG in Scala -

i have dag of words following type: hashmap[string, set[string]]. want build collection of paths through graph. method i've written doesn't behave expect @ all:

def buildchain(wordgraph: hashmap[string, set[string]], path: listbuffer[string], accumchains: listbuffer[listbuffer[string]]): listbuffer[listbuffer[string]] = {   val children = wordgraph(path.last)    (word <- children) {     path += word     if (wordgraph.keyset.contains(word)) buildchain(wordgraph, path, accumchains)     else accumchains += path   }     return accumchains } 

when pass in graph:

map("chow" -> set("how", "cho", "cow"), "how" -> set("ho", "ow"), "cho" -> set("ho"), "cow" -> set("ow"))

i expect get:

listbuffer(listbuffer("chow", "how", "ho"), listbuffer("chow", "how", "ow"), listbuffer("chow", "cho", "ho"), listbuffer("chow", "cow", "ow"))

when start @ "chow".

instead i'm getting this:

listbuffer(listbuffer(chow, how, ho, ow, cho, ho, cow, ow), listbuffer(chow, how, ho, ow, cho, ho, cow, ow), listbuffer(chow, how, ho, ow, cho, ho, cow, ow), listbuffer(chow, how, ho, ow, cho, ho, cow, ow))

and can't figure out why. i'm sure it's simple, i'm missing right now.

here simple solution, changed little bit param types think immutable types enough:

def _buildchain(wordgraph: map[string, set[string]], path: string): list[list[string]] = {    wordgraph.get(path) match {     case some(w) =>  w.tolist.flatmap(_buildchain(wordgraph, _).map(path :: _))      case none =>  list(list(path))   } }  def buildchain(wordgraph: map[string, set[string]], path: list[string]): list[list[string]] = path.flatmap(_buildchain(wordgraph, _))    val = _buildchain( map("chow" -> set("how", "cho", "cow"), "how" -> set("ho", "ow"), "cho" -> set("ho"), "cow" -> set("ow")), "chow") println(a) val b = buildchain( map("chow" -> set("how", "cho", "cow"), "how" -> set("ho", "ow"), "cho" -> set("ho"), "cow" -> set("ow")), list("chow", "how")) println(b) 

the output is:

list(list(chow, how, ho), list(chow, how, ow), list(chow, cho, ho), list(chow, cow, ow))   list(list(chow, how, ho), list(chow, how, ow), list(chow, cho, ho), list(chow, cow, ow), list(how, ho), list(how, ow))