CODEWITHSUNDEEP
listscalasplitfunctional-programmingpredicate
sveri
sveri

Reputation: 1389

Splitting a list into two lists in scala

I have a list containing something like:

val lines: List[String] = List("bla blub -- id_1", "sdkfjdf -- id_2", "blubber blab -- id_1", "foo -- id_3", "ieriuer -- id_2", "bar -- id_3")

So basically the list contains an identifier which exists exactly twice (id_x) and a string which belongs to one of the identifiers.

I want to split that one list into two lists which then each contains a unique set of id_s with their belonging strings, like this:

l1("bla blub -- id_1", "sdkfjdf -- id_2", "foo -- id_3") 
l2("blubber blab -- id_1", "ieriuer -- id_2", "bar -- id_3")

How would i do that in a functional way?

Best Regards, Sven

Upvotes: 3

Views: 2241

Answers (2)

Luigi Plinge
Luigi Plinge

Reputation: 51109

lines.groupBy(_.split(" -- ")(1)).toList.map(_._2).transpose

That's the rough and ready way to do it; in reality if you want to do something more with this data it'll probably be better to parse the items into a case class, a la:

case class Item(id: String, text: String)
val items = for {
  line <- lines
  Array(text, id) = line.split(" -- ")
} yield Item(id, text)

then do the same as above, except groupBy(_.id), and conveniently sortBy(_.id) as well.

Upvotes: 3

4lex1v
4lex1v

Reputation: 21567

How about this solution? 

lines.groupBy(_.takeRight(3)).map(_._2).foldLeft((List.empty[String], List.empty[String])) { 
  (acc, elem) => elem match {
    case left :: right :: Nil =>
      (left :: acc._1, right :: acc._2)
    case Nil => acc
  }
}

res2: (List[String], List[String]) = (List(bla blub -- id_1, sdkfjdf -- id_2, foo -- id_3),List(blubber blab -- id_1, ieriuer -- id_2, bar -- id_3))

Upvotes: 1

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