import scala.collection.mutable

type KeyType = Long

def grouping(xs: mutable.Map[KeyType, Option[String]], box: Int): List[List[(KeyType, Option[String])]] = {
  (for ((x, count) <- xs.toList.zipWithIndex) yield (count, x)).groupBy(x => x._1 % box).map(x => x._2.map(c => c._2)).toList
}

def mergeGroup(xs: List[List[(KeyType, Option[String])]]): mutable.Map[KeyType, Option[String]] = {
  def flatten(ls: List[_]): List[_] = ls flatMap {
    case i: List[_] => flatten(i)
    case e => List(e)
  }
  collection.mutable.Map(flatten(xs).map{case(k, v) => (k, v)}: _*).asInstanceOf[mutable.Map[KeyType, Option[String]]]
}

val xs: mutable.Map[KeyType, Option[String]] = mutable.Map(
  (24, Some("flag")),
  (83, Some("setup")),
  (89, Some("fighter")),
  (94, Some("curiosities")),
  (114, Some("strong")),
  (133, Some("brutish")),
  (177, Some("blockade")),
  (247, Some("fort")),
  (299, Some("bad")),
  (302, Some("burial")),
  (317, Some("contestant")),
  (329, Some("anonymous")),
  (337, Some("cube")),
  (341, Some("elimination")),
  (345, Some("contractual")),
  (434, Some("everlasting")),
  (445, Some("daydreamer")),
  (468, Some("femur")),
  (475, Some("decipherer")),
  (479, Some("serpent")),
  (602, Some("chain")),
  (604, Some("rum")),
  (612, Some("terminus")),
  (623, Some("degrading")),
  (640, Some("loneliness")),
  (649, Some("blob")),
  (685, Some("land")),
  (692, Some("confidential")),
  (696, Some("herd")),
  (699, Some("beyond"))
)


val groupedData: List[List[(KeyType, Option[String])]] = grouping(xs, 5)
groupedData.map(println)

val mergedData: mutable.Map[KeyType, Option[String]] = mergeGroup(groupedData)

println(xs)
println(mergedData)