Facebook's how to crush your coding interview example in Scala.

FBSampleApp.scala

object FBSampleApp extends App {
  // sample implementations
  def nearbyChars(c: Char): Set[Char] = Set(c + 0, c + 1).map(_.toChar)
  def isWord(s: String): Boolean = true

  def distSoFar(a: String, b: String) = a.zip(b).count(ab => ab._1 != ab._2)

  def nearbyWords(input: String, maxDist: Int = 1): Set[String] =
    input.foldLeft(Set("")) { (words, char) =>
      for {
        c <- nearbyChars(char)
        w <- words
        word = w + c
        if distSoFar(input, word) <= maxDist
      } yield word
    }.filter(isWord)

  println(nearbyWords("Hello"))
}