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NQueensVisualizer.java
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NQueensVisualizer.java
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import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;
public class NQueensVisualizer extends JFrame {
private int size;
private int delay;
private JTextField[][] cells;
private int[][] board;
private boolean solving;
private JButton startStopButton;
private JButton nextSolutionButton;
private int solutionCount;
private List<int[][]> solutions;
public NQueensVisualizer() {
setTitle("N-Queens Visualizer");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(new BorderLayout());
size = getSizeFromUser();
delay = getSpeedFromUser();
cells = new JTextField[size][size];
board = new int[size][size];
solutions = new ArrayList<>();
solving = false;
solutionCount = 0;
JPanel gridPanel = new JPanel();
gridPanel.setLayout(new GridLayout(size, size));
for (int row = 0; row < size; row++) {
for (int col = 0; col < size; col++) {
cells[row][col] = new JTextField();
cells[row][col].setHorizontalAlignment(JTextField.CENTER);
cells[row][col].setFont(new Font("Arial", Font.BOLD, 20));
cells[row][col].setEditable(false);
cells[row][col].setBackground((row + col) % 2 == 0 ? Color.WHITE : Color.BLACK);
cells[row][col].setForeground((row + col) % 2 == 0 ? Color.BLACK : Color.WHITE);
gridPanel.add(cells[row][col]);
board[row][col] = 0;
}
}
add(gridPanel, BorderLayout.CENTER);
JPanel buttonPanel = new JPanel();
buttonPanel.setLayout(new GridLayout(1, 2));
startStopButton = new JButton("Start");
startStopButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
if (solving) {
solving = false;
startStopButton.setText("Start");
} else {
solving = true;
startStopButton.setText("Stop");
new Thread(new Runnable() {
@Override
public void run() {
solvePuzzle();
}
}).start();
}
}
});
buttonPanel.add(startStopButton);
nextSolutionButton = new JButton("Next Solution");
nextSolutionButton.setEnabled(false);
nextSolutionButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
solving = true;
new Thread(new Runnable() {
@Override
public void run() {
clearBoard();
solutionCount++;
solvePuzzle();
}
}).start();
}
});
buttonPanel.add(nextSolutionButton);
add(buttonPanel, BorderLayout.SOUTH);
setSize(600, 600);
}
private int getSizeFromUser() {
String input = JOptionPane.showInputDialog(this, "Enter the number of queens:", "N-Queens", JOptionPane.QUESTION_MESSAGE);
return Integer.parseInt(input);
}
private int getSpeedFromUser() {
String input = JOptionPane.showInputDialog(this, "Enter the speed in milliseconds:", "Speed", JOptionPane.QUESTION_MESSAGE);
return Integer.parseInt(input);
}
private void solvePuzzle() {
if (findSolution()) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
JOptionPane.showMessageDialog(NQueensVisualizer.this, "N-Queens Solved! Solution #" + solutionCount, "Success", JOptionPane.INFORMATION_MESSAGE);
nextSolutionButton.setEnabled(true);
}
});
} else {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
JOptionPane.showMessageDialog(NQueensVisualizer.this, "No more solutions exist for the given N-Queens board.", "Error", JOptionPane.ERROR_MESSAGE);
nextSolutionButton.setEnabled(false);
}
});
}
solving = false;
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
startStopButton.setText("Start");
}
});
}
private boolean findSolution() {
return solveNQueens(0);
}
private void clearBoard() {
for (int row = 0; row < size; row++) {
for (int col = 0; col < size; col++) {
cells[row][col].setText("");
cells[row][col].setBackground((row + col) % 2 == 0 ? Color.WHITE : Color.BLACK);
cells[row][col].setForeground((row + col) % 2 == 0 ? Color.BLACK : Color.WHITE);
board[row][col] = 0;
}
}
}
private boolean isSafe(int row, int col) {
for (int i = 0; i < col; i++) {
if (board[row][i] == 1) {
return false;
}
}
for (int i = row, j = col; i >= 0 && j >= 0; i--, j--) {
if (board[i][j] == 1) {
return false;
}
}
for (int i = row, j = col; j >= 0 && i < size; i++, j--) {
if (board[i][j] == 1) {
return false;
}
}
return true;
}
private boolean solveNQueens(int col) {
if (col >= size) {
if (!isDuplicateSolution()) {
storeSolution();
return true;
}
return false;
}
for (int i = 0; i < size; i++) {
if (!solving) {
return false;
}
if (isSafe(i, col)) {
board[i][col] = 1;
updateGUI(i, col, true);
delay(delay); // Delay to visualize steps
if (solveNQueens(col + 1)) {
return true;
}
board[i][col] = 0;
updateGUI(i, col, false);
delay(delay); // Delay to visualize steps
}
}
return false;
}
private void storeSolution() {
int[][] solution = new int[size][size];
for (int i = 0; i < size; i++) {
System.arraycopy(board[i], 0, solution[i], 0, size);
}
solutions.add(solution);
}
private boolean isDuplicateSolution() {
for (int[][] solution : solutions) {
if (areBoardsEqual(solution, board)) {
return true;
}
}
return false;
}
private boolean areBoardsEqual(int[][] board1, int[][] board2) {
for (int i = 0; i < size; i++) {
for (int j = 0; j < size; j++) {
if (board1[i][j] != board2[i][j]) {
return false;
}
}
}
return true;
}
private void updateGUI(int row, int col, boolean placeQueen) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
if (placeQueen) {
cells[row][col].setText("Q");
cells[row][col].setBackground(Color.ORANGE);
cells[row][col].setForeground(Color.BLACK);
} else {
cells[row][col].setText("");
cells[row][col].setBackground((row + col) % 2 == 0 ? Color.WHITE : Color.BLACK);
cells[row][col].setForeground((row + col) % 2 == 0 ? Color.BLACK : Color.WHITE);
}
}
});
}
private void delay(int milliseconds) {
try {
Thread.sleep(milliseconds);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
NQueensVisualizer visualizer = new NQueensVisualizer();
visualizer.setVisible(true);
}
});
}
}