Scala将Map [String，List [String]]转换为Map [String，String]

Question

Would someone be able to help me convert Map[String, List[String]] to a Map[String, String] in scala?

Here is the Map[String, List[String]] as follows:

val pets: Map[String, List[String]] = Map(
    "home" -> List("cat", "dog", "fish"),
    "farm" -> List("cow", "horse"), 
    "wild" -> List("tiger", "elephant")
)

That needs to be converted to Map[String, String] as follows:

val pets2: Map[String, String] = Map(
    "home" -> "cat",
    "home" -> "dog",
    "home" -> "fish",
    "farm" -> "cow",
    "farm" -> "horse",
    "wild" -> "tiger",
    "wild" -> "elephant"
)

Answer 1

As mentioned before each key in a Map is unique.

That said, what you can do is convert the map to a sequence of tuples:

pets.toSeq.flatMap { case (key, list) => list.map(key -> _) }

will give you:

ArrayBuffer(
  (home,cat), 
  (home,dog), 
  (home,fish), 
  (farm,cow), 
  (farm,horse), 
  (wild,tiger), 
  (wild,elephant)
)

Answer 2

地图不能有重复的键。