// towers.java
// solves Towers of Hanoi puzzle
// to run this program: C>java TowersApp
////////////////////////////////////////////////////////////////
class TowersApp
   {
   static int nDisks = 3;
       static final String inMore = "   ";
   public static void main(String[] args)
      {
	  if (args.length > 0)
          {
	      nDisks = Integer.parseInt(args[0]);
	  }

	  doTowers(nDisks, 'A', 'B', 'C', "");

      }
   //-----------------------------------------------------------
   public static void doTowers(int topN,
                               char src, char inter, char dest,
			       String indent)
      {
      System.out.println(indent + topN + ": "+ "Task: Move " + nList(topN)  + 
                            " from " + src + " to "+ dest);
      if(topN==1)
         System.out.println(indent + topN + ": " + "Disk 1 from " + src + " to "+ dest);
      else
         {
         doTowers(topN-1, src, dest, inter, indent + topN+">>> ");   // src to inter

         System.out.println(indent + topN + ": " +  "Disk " + topN +   // move bottom
                            " from " + src + " to "+ dest);
         doTowers(topN-1, inter, src, dest, indent + topN+"<<< ");   // inter to dest
         }
      System.out.println(indent + topN + ": " + "Task done " + nList(topN));  
      }
       static String nList(int n) {
	   StringBuilder s = new StringBuilder("{");
	   while (n > 1)
	       s.append(n-- +",");
	   s.append("1}");
	   return s.toString();
       }
//-------------------------------------------------------------
   }  // end class TowersApp
////////////////////////////////////////////////////////////////