TowersOfHanoi.scala

import scala.Range

class TowersOfHanoi(val n: Int) {
    def hanoi(m: Int, from: Int, to: Int, work: Int, s: Array[List[Int]]) {
        if (m == 1) {
            s(to) = s(from).head::s(to)
            s(from) = s(from).tail
            println(disp(s.toList.map(_.reverse)))
        } else {
            hanoi(m-1, from, work, to, s)
            hanoi(1, from, to, work, s)
            hanoi(m-1, work, to, from, s)
        }
    }

    def disp(a: List[List[Int]]): String = {
        if (a == List(Nil, Nil, Nil)) {
            "-" * (n * 2 * 3) + "\n"
        } else {
            disp(a.map(x => if (x == Nil) Nil else x.tail)) + "\n" + 
            a.map(x => if (x == Nil) 0 else x.head).map(
                x => " " * (n-x) + " ■ ■" * x + " " * (n-x) + " ").mkString
        }
    }

    def start() {
        val s = Array(Range(1, n+1).toList, Nil, Nil)
        hanoi(n, 0, 2, 1, s)
    }
}

object TowersOfHanoiApp extends App
{
    new TowersOfHanoi(4).start
}