The shuttle puzzle problem..

Question

Hi guys;
for those raedy to rise challenges i present this problem... Any ideas to solve it are welcomed..some code would be a generous action from your part...
SHUTTLE PUZZLE
The SHUTTLE PUZZLE of size 3
consists of 3 white marbles, 3 black
marbles, and a strip of wood with 7 holes.
The marbles of the same color are placed
in the holes at the opposite ends of the
strip, leaving the center hole empty.
INITIAL STATE: WWW BBB
GOAL STATE: BBB WWW
To solve the shuttle puzzle use only two
types of moves. Move 1 marble 1 space
(into the empty hole) or jump 1 marble
over 1 marble of the opposite color (into
the empty hole). You may not back up,
and you may not jump over 2 marbles.
A Shuttle Puzzle of size N consists of N
white marbles and N black marbles and
2N+1 holes.
Write a program that will solve the
SHUTTLE PUZZLE for any size N(*10)
and display the board after each move.
Use W to represent a white marble and B
to represent a black marble and a blank to
represent the empty hole. Test your
program for N=3 and N=4.
Sample Run
N = 3
WWW BBB
WWWB BB
WW BWBB
W WBWBB
WBW WBB
WBWBW B
WBWBWB
WBWB BW
WB BWBW
BWBWBW
B WBWBW
BBW WBW
BBWBW W
BBWB WW
BB BWWW
BBB WWW

Answer 1

my friend , here is my own program for the Shutle problem...
try it and tell me if something is wrong...
cheers.
* Created on 23 f�vr. 2004
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* @author user
* To change the template for this generated type comment go to
* Window>Preferences>Java>Code Generation>Code and Comments
import java.io.*;
import java.util.*;
public class Shuttle {
     static int N=3;
     static int ln= 2*N+1;
     static int p=(int) Math.pow(2,N+1);
     static String[] a= new String[ln];
     static boolean shifted= false;
public static void init()throws IOException {
     /*System.out.println("Enter N:");
     String ss= getString();
     N =(int)Integer.parseInt(ss);*/
     System.out.println("Solved shuttle:");
     ln= 2*N+1;
     p=(int) Math.pow(2,N+1);
     a= new String[ln];
     for(int i=0; i<N;i++)
     a="W";
     a[N]=" ";
     for(int i=N+1; i<a.length;i++)
     a[i]="B";
public static String getString() throws IOException
     InputStreamReader isr = new InputStreamReader(System.in);
     BufferedReader br = new BufferedReader(isr);
     String s = br.readLine();
     return s;
public static char getChar() throws IOException{
     String s= getString();
     return s.charAt(0);
public static void print(String[] a){
     for(int i=0;i<a.length;i++)
          System.out.print(a[i]);
          System.out.println();
public static int getHole(String[] a){
     int index=-1;
     for(int i=0;i<a.length;i++){
          if(a[i].equals(" ")){
               index=i;break;
     return index;
public static void swap(String[] a,int i,int j){
     String X=new String();
     X=a[i];
     a[i]=a[j];
     a[j]=X;
public static boolean Done(String[]a){
     boolean done=true;
     for(int i=0;i< N; i++){
          if(!a[i].equals("B")){done=false;break;}
     if(!a[N].equals(" ")){done=false;
     for(int i=N+1; i< a.length;i++){
          if(!a[i].equals("W")){ done=false; break;
     return done;
public static void shuttle(){
     int index=-1;
     //for(int k=0;k<p;k++){
     do{
          print(a);
          index=getHole(a);
          if(index==0){
               if(a[index+1].equals("B"))swap(a,index,index+1);
               else if(a[index+1].equals("W")&& a[index+2].equals("B")) swap(a,index,index+2);
               //else if(a[index+1].equals("W")&& a[index+2].equals("B")) swap(a,index,index+2);
          else if(index==a.length-1){
               if(a[index-1].equals("B")&&a[index-2].equals("W") )swap(a,index,index-2);
               else if(a[index-1].equals("W"))swap(a,index,index-1);
          else if(a[index-1].equals("W")&&a[index+1].equals("B") ){
               if (shifted==false){     swap(a,index,index+1); shifted=true; }
               else if(shifted==true){ swap(a,index,index-1); shifted=false;
               else if(a[index-1].equals("B")&&a[index+1].equals("W")){
                    if(((index+2)<=a.length-1)&& a[index+2].equals("B")) swap(a,index+2,index);
                    else if((index-2>=0)&& a[index-2].equals("W") ) swap(a,index-2,index);
          else if(a[index-1].equals("B")&& a[index+1].equals("B") ){
               if ((index-2>=0)&& a[index-2].equals("W") )swap(a,index-2,index);
               else if (((index+2)<=a.length-1)&& a[index+2].equals("B") ) swap(a,index-2,index);
                    else swap(a,index,index+1);
               else if(a[index-1].equals("W")&& a[index+1].equals("W") ){
                    if (((index +2)<=(a.length-1)) && a[index+2].equals("B")) swap(a,index+2,index);
                    else if ((index -2>=0)&& a[index-2].equals("W") ) swap(a,index-2,index);
                    else swap(a,index,index-1);
          }while(Done(a)==false);
          print(a);
     public static void main(String[] args)throws IOException {
          while (true){
               System.out.println("Enter N:");
               String ss= getString();
               N =(int)Integer.parseInt(ss);
          init();
          shuttle();
          System.out.print("another trial(y/n)?: ");
          char c=getChar();
          if (c=='y')continue;
          else if(c=='n'){System.err.println("Bye!");break;}