The 15 puzzle problem !!!

Question

hey ,
can nebody help me with the code of the autosolve solution of the 15 block puzzle...or atleast the algorithm that is to be used .....????
The program requires the computer to solve the puzzle .....oe move at a time .....
How will i go about it ??

Answer 1

here is the basic code that will help an user play, i am still trying to automate it, if anyone is able to finish it please let me know import java.applet.Applet;
import java.awt.Color;
import java.awt.Event;
import java.awt.Graphics;
// <applet code=puzzle width=100 height=100></applet>
public class Puzzle extends Applet {
     private static final long serialVersionUID = 1L;
     public Piece pieces[] = new Piece[16];
     int i, x, y, currentValue;
     int startX = 50;
     int startY = 50; // start pos of puzzle
     int rowSize = 4;
     int pieceWidth = 50;
     int pieceHeight = 50;
     private int blankPiecePosition;
     Graphics graphics;
     SimplePuzzle simple;
     RandomValue randomValue = new RandomValue(1, 16);
     public void init() {
          graphics = getGraphics();
          /* INITIALIZE THE BLANK PIECES */
          x = startX;
          y = startY;
          for (i = 0; i <= 15; i++) {
               currentValue = randomValue.getRandomValue();
               // currentValue = i+1;
               /* SET THE INITIAL POSTION OF THE BLANK PIECE */
               if (currentValue == 16) {
                    blankPiecePosition = i;
               // pict = getImage(getDocumentBase(),image_name+currentValue+".gif");
               pieces[i] = new Piece(i, currentValue, graphics, x, y, null, this);
               x += 50;
               if (x > 200) {
                    x = 50;
                    y += 50;
          /* CREATE A NEW SIMPLE PUZZLE */
          simple = new SimplePuzzle(15, this);
          resize(pieces[0].width * 6, pieces[0].height * 6);
     public void start() {}
     public void stop() {}
     public boolean mouseDown(Event evt, int x, int y) {
          int rel_x, rel_y;
          int click_piece;
          int cur;
          // FIRST CHECK IF THE POINT IS INSIDE THE PUZZLE
          if (isPointInside(x, y)) {
               // NOW GET THE CLICK PIECE
               rel_x = (int) (x - startX) / pieceWidth;
               rel_y = (int) (y - startY) / pieceHeight;
               click_piece = rel_x + rowSize * rel_y;
               // IF THE CLICK POINT IS IN THE SAME ROW AS THE BLANK PIECE
               if (pieces[blankPiecePosition].sameRow(y)) {
                    if (pieces[click_piece].toLeft(pieces[blankPiecePosition])) {
                         cur = pieces[blankPiecePosition].left;
                         while (cur != pieces[click_piece].left) {
                              pieces[cur].exchangePiece(pieces[blankPiecePosition]);
                              blankPiecePosition = cur;
                              cur = pieces[blankPiecePosition].left;
                              congratulate();
                    } else if (pieces[click_piece].toRight(pieces[blankPiecePosition])) {
                         cur = pieces[blankPiecePosition].right;
                         while (cur != pieces[click_piece].right) {
                              pieces[cur].exchangePiece(pieces[blankPiecePosition]);
                              blankPiecePosition = cur;
                              cur = pieces[blankPiecePosition].right;
                              congratulate();
               } else if (pieces[blankPiecePosition].sameColumn(x)) {
                    if (pieces[click_piece].above(pieces[blankPiecePosition])) {
                         cur = pieces[blankPiecePosition].up;
                         while (cur != pieces[click_piece].up) {
                              pieces[cur].exchangePiece(pieces[blankPiecePosition]);
                              blankPiecePosition = cur;
                              cur = pieces[blankPiecePosition].up;
                              congratulate();
                    } else if (pieces[click_piece].below(pieces[blankPiecePosition])) {
                         cur = pieces[blankPiecePosition].down;
                         while (cur != pieces[click_piece].down) {
                              pieces[cur].exchangePiece(pieces[blankPiecePosition]);
                              blankPiecePosition = cur;
                              cur = pieces[blankPiecePosition].down;
                              congratulate();
          return true;
     private void congratulate() {
          if (simple.isPuzzleComplete()) {
               graphics.drawString("Congratulations!!!", 75, 275);
     public void paint(Graphics g) {
          g.setColor(Color.pink);
          g.fillRect(0, 0, size().width, size().height);
          for (int i = 0; i <= (15); i++) {
               pieces.draw();
     // THIS ROUTINE RETURNS THE VALUE OF A LOCATION
     public int getLocationValue(int arr_loc) {
          return pieces[arr_loc].value.intValue();
     // THIS ROUTINE RETURNS THE VALUE OF THE BLANK LOCATION
     int getBlankLocationValue() {
          return pieces[blankPiecePosition].value.intValue();
     public boolean isPointInside(int x, int y) {
          if ((x >= startX) && (y >= startY)
                    && (x <= startX + rowSize * pieceWidth)
                    && (y <= startY + rowSize * pieceWidth)) {
               return true;
          } else {
               return false;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Image;
public class Piece {
     int width = 50, height = 50;
     int right, left, up, down;
     Integer value; // the value of the Piece
     Integer posX, posY; // the on screen position of the Piece
     Graphics graphics;
     Puzzle objPuzzle;
     public Piece(int index, int val, Graphics agc, int x, int y, Image pict,
               Puzzle objPuzzle) {
          int temp;
          this.objPuzzle = objPuzzle;
          value = new Integer(val);
          graphics = agc;
          posX = new Integer(x);
          posY = new Integer(y);
          // RIGHT
          temp = index + 1;
          if ((temp == 4) || (temp == 8) || (temp == 12) || (temp == 16))
               right = -1;
          else
               right = temp;
          // LEFT
          temp = index - 1;
          if ((temp == 3) || (temp == 7) || (temp == 11))
               left = -1;
          else
               left = temp;
          // UP
          temp = index - 4;
          if ((temp < 0))
               up = -1;
          else
               up = temp;
          // DOWN
          temp = index + 4;
          if ((temp >= 16))
               down = -1;
          else
               down = temp;
     // RETURNS TRUE IF A POINT IS IN THE SAME COL AS y
     public boolean sameColumn(int x) {
          return ((x > posX.intValue()) && (x < posX.intValue() + height));
     // RETURNS TRUE IF A POINT IS IN THE SAME ROW AS x
     public boolean sameRow(int y) {
          return ((y > posY.intValue()) && (y < posY.intValue() + width));
     public boolean toLeft(Piece p) {
          return (posX.intValue() < p.posX.intValue());
     public boolean toRight(Piece p) {
          return (posX.intValue() > p.posX.intValue());
     public boolean above(Piece p) {
          return (posY.intValue() < p.posY.intValue());
     public boolean below(Piece p) {
          return (posY.intValue() > p.posY.intValue());
     public void exchangePiece(Piece blank) {
          Integer temp = value;
          value = blank.value;
          blank.value = temp;
          draw();
          blank.draw();
     public void draw() {
          if (value.intValue() == 16) {
               graphics.setColor(Color.black);
               graphics.fillRect(posX.intValue(), posY.intValue(), width, height);
               graphics.drawRect(posX.intValue(), posY.intValue(), width, height);
          } else {
               graphics.setColor(Color.yellow);
               graphics.fillRect(posX.intValue(), posY.intValue(), width, height);
               graphics.setColor(Color.black);
               graphics.drawRect(posX.intValue(), posY.intValue(), width, height);
               graphics.setFont(new Font("Times", Font.BOLD, 16));
               graphics.drawString(value.toString(), posX.intValue()
                         + (width - graphics.getFontMetrics().stringWidth(
                                   value.toString())) / 2, posY.intValue() + height
                         / 2);
public class SimplePuzzle{
     int win[] = new int[16];
     int winIndex, startIndex;
     Puzzle puzzle;
     SimplePuzzle(int startPosition, Puzzle puz) {
          for (int i = 0; i < 16 ; i++) {
               win[i] = i + 1;
          winIndex = 15;
          startIndex = startPosition;
          puzzle = puz;
     public boolean isPuzzleComplete() {
          if (puzzle.getBlankLocationValue() != winIndex) {
               return false;
          for (int i = 0; i < 16 ; i++) {
               //System.out.println("Loc Value: "+puzzle.getLocationValue(i)+"\tWin: "+win[i]);
               if (puzzle.getLocationValue(i) != win[i]) {
                    return false;
          return true;
// THIS CLASS IS USED TO PROVIDE A UNIQUE RANDOM VALUE FROM
// A RANGE OF VALUES
class RandomValue {
     int value[];
     int total;
     RandomValue(int first, int last) {
          int i;
          total = last - first + 1;
          value = new int[total];
          for (i = 0; i < total; i++) {
               value[i] = first;
               first++;
     int getRandomValue() {
          int i;
          int ret;
          if (total == 0) {
               return -1;
          if (total == 1) {
               total = 0;
               return value[0];
          i = (int) (Math.random() * total);
          ret = value[i];
          total--;
          for (; i < total; i++) {
               value[i] = value[i + 1];
          return ret;