How to correct loop counters for maze algorithm? - algorithm

Question

I have figured out how to move my character around the maze using the algorithm I have written, but the count is not figuring correctly. At the end of each row my character moves up and down several times until the count reaches the specified number to exit the loop, then the character moves along the next row down until it reaches the other side and repeats the moving up and down until the count reaches the specified number again. Can anyone help me find why my count keeps getting off? The algorithm and the maze class I am calling from is listed below.
public class P4 {
public static void main(String[] args) {
// Create maze
String fileName = args[3];
Maze maze = new Maze(fileName);
System.out.println("Maze name: " + fileName);
// Get dimensions
int mazeWidth = maze.getWidth();
int mazeHeight = maze.getHeight();
// Print maze size
System.out.println("Maze width: " + mazeWidth);
System.out.println("Maze height: " + mazeHeight);
int r = 0;
int c = 0;
// Move commands
while (true){
for (c = 0; c <= mazeWidth; c++){
if (maze.moveRight()){
maze.isDone();
c++;
}
if (maze.isDone() == true){
System.exit(1);
}
if (maze.moveRight() == false && c != mazeWidth){
maze.moveDown();
maze.moveRight();
maze.moveRight();
maze.moveUp();
c++;
}
}
for (r = 0; r % 2 == 0; r++){
maze.moveDown();
maze.isDone();
if (maze.isDone() == true){
System.exit(1);
}
}
for (c = mazeWidth; c >= 0; c--){
if (maze.moveLeft()){
c--;
maze.isDone();
System.out.println(c);
}
if (maze.isDone() == true){
System.exit(1);
}
if (maze.moveLeft() == false && c != 0){
maze.moveDown();
maze.moveLeft();
maze.moveLeft();
maze.moveUp();
c--;
}
}
for (r = 1; r % 2 != 0; r++){
maze.moveDown();
maze.isDone();
if (maze.isDone() == true){
System.exit(1);
}
}
}
}
}
public class Maze {
// Maze variables
private char mazeData[][];
private int mazeHeight, mazeWidth;
private int finalRow, finalCol;
int currRow;
private int currCol;
private int prevRow = -1;
private int prevCol = -1;
// User interface
private JFrame frame;
private JPanel panel;
private Image java, student, success, donotpass;
private ArrayList<JButton> buttons;
// Maze constructor
public Maze(String fileName) {
// Read maze
readMaze(fileName);
// Graphics setup
setupGraphics();
}
// Get height
public int getHeight() {
return mazeHeight;
}
// Get width
public int getWidth() {
return mazeWidth;
}
// Move right
public boolean moveRight() {
// Legal move?
if (currCol + 1 < mazeWidth) {
// Do not pass?
if (mazeData[currRow][currCol + 1] != 'D')
{
currCol++;
redraw(true);
return true;
}
}
return false;
}
// Move left
public boolean moveLeft() {
// Legal move?
if (currCol - 1 >= 0) {
// Do not pass?
if (mazeData[currRow][currCol - 1] != 'D')
{
currCol--;
redraw(true);
return true;
}
}
return false;
}
// Move up
public boolean moveUp() {
// Legal move?
if (currRow - 1 >= 0) {
// Do not pass?
if (mazeData[currRow - 1][currCol] != 'D')
{
currRow--;
redraw(true);
return true;
}
}
return false;
}
// Move down
public boolean moveDown() {
// Legal move?
if (currRow + 1 < mazeHeight) {
// Do not pass?
if (mazeData[currRow + 1][currCol] != 'D')
{
currRow++;
redraw(true);
return true;
}
}
return false;
}
public boolean isDone() {
// Maze solved?
if ((currRow == finalRow) && (currCol == finalCol))
return true;
else
return false;
}
private void redraw(boolean print) {
// Wait for awhile
try {
Thread.sleep(500);
} catch (InterruptedException ex) {
Thread.currentThread().interrupt();
}
if (print)
System.out.println("Moved to row " + currRow + ", column " + currCol);
// Compute index and remove icon
int index = (prevRow * mazeWidth) + prevCol;
if ((prevRow >= 0) && (prevCol >= 0)) {
buttons.get(index).setIcon(null);
}
// Compute index and add icon
index = (currRow * mazeWidth) + currCol;
if ((currRow == finalRow) && (currCol == finalCol))
buttons.get(index).setIcon(new ImageIcon(success));
else
buttons.get(index).setIcon(new ImageIcon(student));
// Store previous location
prevRow = currRow;
prevCol = currCol;
}
// Set button
private void setButton(JButton button, int row, int col) {
if (mazeData[row][col] == 'S') {
button.setIcon(new ImageIcon(student));
currRow = row;
currCol = col;
} else if (mazeData[row][col] == 'J') {
button.setIcon(new ImageIcon(java));
finalRow = row;
finalCol = col;
} else if (mazeData[row][col] == 'D') {
button.setIcon(new ImageIcon(donotpass));
}
}
// Read maze
private void readMaze(String filename) {
try {
// Open file
Scanner scan = new Scanner(new File(filename));
// Read numbers
mazeHeight = scan.nextInt();
mazeWidth = scan.nextInt();
// Allocate maze
mazeData = new char[mazeHeight][mazeWidth];
// Read maze
for (int row = 0; row < mazeHeight; row++) {
// Read line
String line = scan.next();
for (int col = 0; col < mazeWidth; col++) {
mazeData[row][col] = line.charAt(col);
}
}
// Close file
scan.close();
} catch (IOException e) {
System.out.println("Cannot read maze: " + filename);
System.exit(0);
}
}
// Setup graphics
private void setupGraphics() {
// Create grid
frame = new JFrame();
panel = new JPanel();
panel.setLayout(new GridLayout(mazeHeight, mazeWidth, 0, 0));
frame.add(Box.createRigidArea(new Dimension(0, 5)), BorderLayout.NORTH);
frame.add(panel, BorderLayout.CENTER);
// Look and feel
try {
UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName());
} catch (Exception e) {
e.printStackTrace();
}
// Configure window
frame.setSize(mazeWidth * 100, mazeHeight * 100);
frame.setTitle("Maze");
frame.setResizable(false);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setAlwaysOnTop(true);
// Load and scale images
ImageIcon icon0 = new ImageIcon("Java.jpg");
Image image0 = icon0.getImage();
java = image0.getScaledInstance(100, 100, Image.SCALE_DEFAULT);
ImageIcon icon1 = new ImageIcon("Student.jpg");
Image image1 = icon1.getImage();
student = image1.getScaledInstance(100, 100, Image.SCALE_DEFAULT);
ImageIcon icon2 = new ImageIcon("Success.jpg");
Image image2 = icon2.getImage();
success = image2.getScaledInstance(100, 100, Image.SCALE_DEFAULT);
ImageIcon icon3 = new ImageIcon("DoNotPass.jpg");
Image image3 = icon3.getImage();
donotpass = image3.getScaledInstance(100, 100, Image.SCALE_DEFAULT);
// Build panel of buttons
buttons = new ArrayList<JButton>();
for (int row = 0; row < mazeHeight; row++) {
for (int col = 0; col < mazeWidth; col++) {
// Initialize and add button
JButton button = new JButton();
Border border = new LineBorder(Color.darkGray, 4);
button.setOpaque(true);
button.setBackground(Color.gray);
button.setBorder(border);
setButton(button, row, col);
panel.add(button);
buttons.add(button);
}
}
// Show window
redraw(false);
frame.setVisible(true);
}
}

Answer 1

One error I can see in your code is that you're incrementing your c counter more often than you should. You start with it managed by your for loop, which means that it will be incremented (or decremented, for the leftward moving version) at the end of each pass through the loop. However, you also increment it an additional time in two of your if statements. That means that c might increase by two or three on a single pass through the loop, which is probably not what you intend.
Furthermore, the count doesn't necessarily have anything obvious to do with the number of moves you make. The loop code will always increase it by one, even if you're repeatedly trying to move through an impassible wall.
I don't really understand what your algorithm is supposed to be, so I don't have any detailed advice for how to fix your code.
One suggestion I have though is that you probably don't ever want to be calling methods on your Maze class without paying attention to their return values. You have a bunch of places where you call isDone but ignore the return value, which doesn't make any sense. Similarly, you should always be checking the return values from your moveX calls, to see if the move was successful or not. Otherwise you may just blunder around a bunch, without your code having any clue where you are in the maze.