riddler_solution

#!/usr/bin/env scala

// This is my solution to http://fivethirtyeight.com/features/who-keeps-the-money-you-found-on-the-floor/
// To run it, just check out the script, make it executable (`chmod +x riddler_solution`), then execute it (`./riddler_solution`)
// You will need the Scala programming language first (if you're on a Mac with Homebrew installed, just `brew install scala`)

import scala.util.Random
import scala.collection.mutable.ListBuffer

class Statistician(val id: Int, rng: Random, winnerLog: ListBuffer[Int], left: => Statistician, right: => Statistician) {
  def tick(): Unit = {
    rng.nextInt(3) match {
      case 0 => winnerLog += id
      case 1 => left.tick()
      case 2 => right.tick()
    }
  }
}

object Scenario extends App {
  val winnerLog = ListBuffer.empty[Int]
  val rng = new Random()

  val me: Statistician = new Statistician(0, rng, winnerLog, colleague4, colleague1)
  lazy val colleague1: Statistician = new Statistician(1, rng, winnerLog, me, colleague2)
  lazy val colleague2: Statistician = new Statistician(2, rng, winnerLog, colleague1, colleague3)
  lazy val colleague3: Statistician = new Statistician(3, rng, winnerLog, colleague2, colleague4)
  lazy val colleague4: Statistician = new Statistician(4, rng, winnerLog, colleague3, me)

  val iterations = 1000000
  (0 until iterations).foreach(_ => me.tick())
  val myWins = winnerLog.toList.count(_ == me.id)

  println(f"I win ${myWins.toDouble / iterations * 100}%1.2f%% of the time")
}

Scenario.main(args)