Simulate attack scenarios in a classic Risk game.

risk

#!/usr/bin/env scala

import math._
import scala.util.Random

val Iterations = 100000
val MaxAttackers = 15
val MaxDefenders = 15

/** Randomly simulates a complete attack (until there are either no attackers or defenders left).
  * Returns the total number of attacker units lost in the process.
  */
def attack(attackers: Int, defenders: Int): Int = {
  val atts = Array.fill(min(3, attackers))(Random.nextInt(6) + 1).sorted.reverse
  val defs = Array.fill(min(2, defenders))(Random.nextInt(6) + 1).sorted.reverse

  if (attackers == 0 || defenders == 0) {
    attackers
  } else {
    val attackLosses: Int = atts.zip(defs).map { case (a, d) =>
      if (a > d) 0 else 1
    }.sum
    val defenseLosses = math.min(atts.length, defs.length) - attackLosses

    attack(attackers - attackLosses, defenders - defenseLosses)
  }
}

//fill results
val results =
  for(attackers <- 0 until MaxAttackers) yield {
    for (defenders <- 0 until MaxDefenders) yield {
      (0 until Iterations).map(_ => attack(attackers, defenders)).sum.toDouble / Iterations
    }
  }

println("Expected remaining attacker units")
println("att\\def\t|" + (0 until MaxDefenders).mkString("\t"))
println("========" + "="*8 * (MaxDefenders + 1))
for (i <- 0 until MaxAttackers) {
  println("\t|")
  //if (i % 2 != 0) print("\u001B[7m")
  //else print("\u001B[0m")
  print(s"$i\t|")
  for (j <- 0 until MaxDefenders) {
    print(results(i)(j) formatted "%.2f")
    print("\t")
  }
  println("")
}