如何在scala中将Map [Map [String，Int]，Int]转换为Map [String，Int]？

Question

Eg. Map[Map[String,Int],Int] I need to convert it into Map[String,Int] ie Int in value part of inner map is replaced with Int in value part of outer map.

For example:

val innerMap = Map("a"->1)
val outerMap = Map(innerMap, 2)

Required result:

resultMap = Map("a"->2)

Answer 1

Even though you haven't answered my question about duplicate String values, I'm going to guess that what you want is something like this.

val mmsii :Map[Map[String,Int],Int] =
  Map(Map("a"->1)->11,Map("b"->2)->22)

mmsii.flatMap{case (m,v) => m.keys.map(_ -> v)}

Or, using the sometimes friendlier for comprehension:

for {
  (m,v) <- mmsii
  (k,_) <- m
} yield k->v

Keep in mind, if there are duplicate String keys then only one String->Int pair will be retained and the others will be lost.

Answer 2

You can leverage this solution to your problem

    val anotherMap = Map(Map("a" -> 1) -> 10, Map("b" -> 2) -> 11, Map("c" -> 3) -> 12)

    anotherMap.flatMap {
  case (keyMap, value) =>
    keyMap map {
      case (k, _) => Map(k -> value)
    }
}

// res0: scala.collection.immutable.Iterable[scala.collection.immutable.Map[String,Int]] = List(Map(a -> 10), Map(b -> 11), Map(c -> 12))

Answer 3

Pretty much the same as @jwvh 's solution, just a little more explicit

val nestedMap: Map[Map[String, Int], Int] = Map(
  Map("k1" -> 1) -> 11,
  Map("k2" -> 2, "k3" -> 3) -> 22
)

val unnestedMap: Map[String, Int] = nestedMap.flatMap { (outerTuple: (Map[String, Int], Int)) =>
  val innerMap: Map[String, Int] = outerTuple._1
  val commonVal: Int = outerTuple._2
  innerMap.map { (innerTuple: (String, Int)) =>
    (innerTuple._1 -> commonVal)
  }
}
print(unnestedMap)