# Building a Tree from Breadcrumbs

I need to transform

List("home", "mens", "clothing", "jackets")


into

List(
"/home",
"/home/mens",
"/home/mens/clothing",
"/home/mens/clothing/jackets"
)


This is what I have so far:

val nodes = Array("home", "mens", "clothing", "jackets")
val (rootNode, otherNodes) = nodes.splitAt(1)
val tree = otherNodes.foldLeft(rootNode) { (list, token) =>
list :+ (list.last + "/" + token)
}


What do you think? any obvious problems?

It looks like you need a variation of the prefix sum algorithm applied to your list. In Scala this can be accomplished with scan:

val xs = List("home", "mens", "clothing", "jackets")
xs.scan("")(_ + "/" + _).tail

• Very nice! I didn't know about scan – user78169 Mar 17 '16 at 3:44

I think you don't need to split the nodes to run this correctly..

consider:

val tree = (nodes.foldLeft("") { (list, token) =>
list :+ (list.last + "/" + token)
}).tail


I could also imagine extracting the current binary operator into a separate function.

Aside from that this is really nice and clean