Code Golf: Towers of Hanoi

Answer 1

Here's a starter for 10, in Scala, revised a few times. I don't know of any issues, and I have no other ideas for further reducing the moves

Runs as a Scala script.

Bits of this are quite elegant (IMO) but other bits are an ugly hack

Shortest code (but non-optimal moves), tracking position of disks rather than list of disks on rods (idea shamelessly stolen from the Perl solution)

 val r=args(0).split(",",-1);var d=Map{{for(q<-0 to 2 if""!=r(q);n<-r(q).split('-').map{_.toInt})yield(n,q+1)}:_*};val n=d.max._1;var m="";def s(f:Int,t:Int,n:Int):Unit=if(n!=0&&f!=t){s(f,6-f-t,n-1);d=d+(n->t);m=m+","+f+t;s(6-f-t,t,n-1)};for(c<- 2 to n)s(d(1),d(c),c-1);if(m=="")s(d(1),d(1)%3+1,n);println(m.tail.replaceAll("(.),?\\1",""))

Puzzle is taken from the command line.

338 bytes. Not too shabby since this is a statically typed language, and still relatively readable (if you replace ; with newlines)

Readable version follows (with more optimal moves)

val rods = args(0).split(",", -1);
var diskLocation = Map{
  {
    for (rod <-0 to 2 if rods(rod).nonEmpty;
         n <-rods(rod).split('-').map{_.toInt})
      yield(n, rod + 1)
  }:_*
}

val nDisks = diskLocation.max._1

var moves = ""

def moveTower(start:Int, end:Int, n:Int):Unit = 
  if (n != 0) {
    val other = 6 - start - end
    moveTower(start, other, n - 1)
    moveDisk(n, end)
    moveTower(other, end, n - 1)
  }

def moveDisk(n:Int, end:Int) = {
  moves = moves + "," + diskLocation(n) + end
  diskLocation = diskLocation.updated(n, end);
}

for (c <- 2 to nDisks) {
  var firstLocation = diskLocation(1)
  var nextLocation = diskLocation(c)
  if (firstLocation != nextLocation) {
    if (c != nDisks) {
      val diskAfter = diskLocation(c + 1)
      if (diskAfter != firstLocation && diskAfter != nextLocation) {
        moveDisk(c, diskAfter)
        nextLocation = diskAfter
      }
    }
    moveTower(diskLocation(1), diskLocation(c), c - 1);
  }
}

if (moves == "")
  moveTower(diskLocation(1), diskLocation(1)%3 + 1, nDisks)

println(moves.tail.replaceAll("(.),?\\1",""))