Merge maps by key

Question

Say I have two maps:

val a = Map(1 -> \"one\", 2 -> \"two\", 3 -> \"three\")
val b = Map(1 -> \"un\", 2 -> \"deux\", 3 -> \"trois\")
         


        

Answer 1

val a = Map(1 -> "one", 2 -> "two", 3 -> "three")
val b = Map(1 -> "un", 2 -> "deux", 3 -> "trois")

val c = a.toList ++ b.toList
val d = c.groupBy(_._1).map{case(k, v) => k -> v.map(_._2).toSeq}
//res0: scala.collection.immutable.Map[Int,Seq[java.lang.String]] =
        //Map((2,List(two, deux)), (1,List(one, un), (3,List(three, trois)))