Scala convert Map[String, Set[String]] to Map[(String, String), Option[Double]]

Question

I was thinking of a way to create a tuple consisting of the String key from the map along with each of the Strings from the Set together as tuple that form the key in a new map. Value for the new map will be initialized to 0.0.

Ex: If I have to following:

Map[ USA, Set[CA, NY, WA]]

I want to create a new map from this which looks like:

Map[(USA,CA) -> 0.0, (USA,NY) -> 0.0, (USA,WA) -> 0.0]

I am able to create a Map[String, String] but I was hoping to get some help in creating the tuple key.

rstar · Accepted Answer · 2017-07-12 20:32:26Z

4

Map("USA" -> Set("CA", "NY", "WA")) flatMap { case (k, set) => set.map((k, _) -> 0.0) }

answered Jul 12, 2017 at 20:32

rstar

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sheunis · Accepted Answer · 2017-07-12 20:26:58Z

1

val myMap = Map("USA" -> Set("CA", "NY", "WA"))

val newMap = myMap.foldLeft(Map[(String, String), Double]()) {
  case (acc, (key, values)) => {
    acc ++ (for {
      value <- values
    } yield (key, value) -> 0.0)
  }
}

answered Jul 12, 2017 at 20:26

sheunis

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