Scrabble.scala

object Scrabble extends App {
  import scala.io.Source

  val words = Source.fromFile("/usr/share/dict/words").getLines.toStream

  val primes: Stream[Int] =
    2 #:: Stream.from(3, 2).filter(i => primes.takeWhile(p => p * p <= i).forall(p => i % p > 0))

  val letterCounts = words.foldLeft(Map.empty[Char, Long].withDefault(_ => 0L)) { case (counts, word) =>
    word.toLowerCase.filter(_.isLetter).foldLeft(counts) { case (counts2, c) =>
      counts2.updated(c, counts2(c) + 1)
    }
  }
  val charPrime = letterCounts.toSeq.sortBy(-_._2).map(_._1).zip(primes).toMap

  def stringPrime(s: String): Long =
    s.toLowerCase.filter(_.isLetter).foldLeft(1L) { case (a, c) => a * charPrime(c) }

  def search(tiles: String, words: Seq[String]): Seq[String] = {
    val tilesPrime = stringPrime(tiles)
    words
      .filter(_.length <= tiles.length)
      .filter(word => tilesPrime % stringPrime(word) == 0)
  }

  search("abcdefghi", words).foreach(println)
}