それぞれ異なる色の、５つの建物が...

fish.scala

// http://d.hatena.ne.jp/kmizushima/20090629/1246212207
// 写経+α(関数少し変えただけ)
// 改行の練習になった気がする．

object Houses extends Enumeration{
  val red = Value("Red")
  val white = Value("White")
  val green = Value("Green")
  val yellow = Value("Yellow")
  val blue = Value("Blue")
}

object Countries extends Enumeration{
  val japan = Value("Japan")
  val usa = Value("America")
  val china = Value("China")
  val brazil = Value("Brazil")
  val italy = Value("Italy")
}

object Drinks extends Enumeration{
  val milk = Value("Milk")
  val tea = Value("Tea")
  val coffee = Value("Coffee")
  val water = Value("Water")
  val beer = Value("Beer")
}

object Tabacoes extends Enumeration{
  val mildseven = Value("MildSeven")
  val sevenstar = Value("SevenStar")
  val marlboro = Value("Marlboro")
  val hope = Value("Hope")
  val lark = Value("Lark")
}

object Pets extends Enumeration{
  val cat = Value("Cat")
  val dog = Value("Dog")
  val bird = Value("Bird")
  val horse = Value("Hourse")
  val fish = Value("Fish")
}

case class Info(house: Houses.Value, country: Countries.Value, drink: Drinks.Value, tabaco: Tabacoes.Value, pet: Pets.Value)

// このc2って一体なんなんだ… 引数無しの関数でもないし，Booleanになるもの？
def -->(c1: Boolean, c2: => Boolean): Boolean = if (c1) c2 else true

def select[A](ls: List[A]): List[(A, List[A])] = ls map {n => (n, ls filterNot {_ == n})}

def forallWithIndex[A](arr: Array[A])(pred: (A, Int) => Boolean): Boolean = {
  arr.zipWithIndex.forall(n => pred(n._1, n._2))
}

def solve(hs: List[Houses.Value], cs: List[Countries.Value], ds: List[Drinks.Value],
	  ts: List[Tabacoes.Value], ps: List[Pets.Value])(f: Array[Info] => Unit) = {
  def solve_(hs: List[Houses.Value], cs: List[Countries.Value], ds: List[Drinks.Value],
    	     ts: List[Tabacoes.Value], ps: List[Pets.Value], acc: List[Info]): Unit = {
    hs match {
      case _ :: _ => {
	for{(h, hR) <- select(hs)
	    (c, cR) <- select(cs) if -->(c == Countries.japan, h == Houses.red)
	    (d, dR) <- select(ds) if -->(c == Countries.china, d == Drinks.tea)
			   if -->(h == Houses.green, d == Drinks.coffee)
	    (t, tR) <- select(ts) if -->(h == Houses.yellow, t == Tabacoes.mildseven)
			   if -->(t == Tabacoes.hope, d == Drinks.beer)
			   if -->(c == Countries.brazil, t == Tabacoes.lark)
	    (p, pR) <- select(ps) if -->(c == Countries.usa, p == Pets.dog)
			   if -->(t == Tabacoes.sevenstar, p == Pets.bird)
	  }{solve_(hR, cR, dR, tR, pR, Info(h,c,d,t,p) :: acc)
	  }
      }
      case Nil => {
	val ps = acc.toArray
	if (ps(0).country == Countries.italy
	    && ps(2).drink == Drinks.milk
	    && forallWithIndex(ps){(p, i) =>
	      ( -->(i > 0 && p.house == Houses.white, ps(i-1).house == Houses.green)
	       && -->(p.tabaco == Tabacoes.marlboro,
		      (i > 0 && ps(i-1).pet == Pets.cat) ||
		      (i < ps.length - 1 && ps(i+1).pet == Pets.cat))
	       && -->(p.tabaco == Tabacoes.marlboro,
		      (i > 0 && ps(i-1).drink == Drinks.water) ||
		      (i < ps.length - 1 && ps(i+1).drink == Drinks.water))
	       && -->(p.house == Houses.blue,
		      (i > 0 && ps(i-1).country == Countries.italy) ||
		      (i < ps.length - 1 && ps(i+1).country == Countries.italy))
	       && -->(p.pet == Pets.horse,
		      (i > 0 && ps(i-1).tabaco == Tabacoes.mildseven) ||
		      (i < ps.length -1 && ps(i+1).tabaco == Tabacoes.mildseven)))
				  }
	  ){ f(ps) } 
      }
    }
  }
  solve_(hs,cs,ds,ts,ps,Nil)
}

lazy val output = {
  solve(Houses.values.toList,
	Countries.values.toList,
	Drinks.values.toList,
	Tabacoes.values.toList,
	Pets.values.toList){ ps =>
	  println(ps.toList)}
}