The Coupon collector's problem implementation in Scala: http://en.wikipedia.org/wiki/Coupon_collector's_problem

CouponCollectorUntilSuccess.scala

package com.liveperson.predictivedialer.examples.misc

import scala.util.Random
import scala.collection.mutable
import com.liveperson.predictivedialer.common.utils.TraversableWithStatistics._

/**
 * Created with IntelliJ IDEA.
 * User: mishaelr
 * Date: 1/16/14
 * Time: 1:47 PM
 */
object CouponCollectorUntilSuccess extends App{

  val rand = new Random()

  require(args.length == 2,
    """Coupon Collector: Usage: there should be two arguments:
      |The total number of possible coupons.
      |The number of experiment repeats.""".stripMargin)

  val (totalNumCoupons, numOfRepeats) = (args(0).toInt, args(1).toInt)
  val experimentsResults = List.fill(numOfRepeats)(collectCouponsUntilSuccess)

  println(
    """Coupon Collector: The mean number of collected coupons until success was %s, the variance was %s.
      |The total number of possible coupons %s.
      |The number of experiments was %s.
      |nlog(n) = %s""".format(experimentsResults.mean, experimentsResults.variance, totalNumCoupons, numOfRepeats, totalNumCoupons * math.log(totalNumCoupons)).stripMargin)

  def collectCouponsUntilSuccess = {
    val couponsIterator = Iterator.continually(rand.nextInt(totalNumCoupons)).zipWithIndex
    val collectedCoupons = mutable.Set[Int]()
    val firstCouponOfSuccess = couponsIterator.find{case (coupon, index) =>
      collectedCoupons += coupon
      collectedCoupons.size == totalNumCoupons
    }
    firstCouponOfSuccess.get._2 + 1 //th +1 is due to index to length
  }
}