Sudoku solver into a User Interface (UI) application

[Ansari-Shamaila]

How It Works:
UI Creation: The SudokuUI class creates a 9x9 grid using JTextField for user input.
Input Parsing: The parseInput() method reads the values from the text fields and converts them to an integer array (board).
Sudoku Solving: When the "Solve" button is clicked, the solveSudoku() method is triggered, which solves the puzzle using the SudokuOptimized class and displays the solution in the UI.
Output Display: After solving, the solution is displayed in the grid, and a message dialog informs the user if the puzzle was solved or unsolvable.

import javax.swing.;
import java.awt.;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class SudokuUI extends JFrame {

private static final int SIZE = 9; // Size of the Sudoku grid private JTextField[][] grid = new JTextField[SIZE][SIZE]; // 9x9 JTextFields for the grid private int[][] board = new int[SIZE][SIZE]; // Sudoku board public SudokuUI() { setTitle("Sudoku Solver"); setSize(600, 600); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setLayout(new BorderLayout()); // Create the Sudoku grid panel JPanel gridPanel = new JPanel(new GridLayout(SIZE, SIZE)); for (int row = 0; row < SIZE; row++) { for (int col = 0; col < SIZE; col++) { grid[row][col] = new JTextField(); grid[row][col].setHorizontalAlignment(JTextField.CENTER); grid[row][col].setFont(new Font("Arial", Font.BOLD, 20)); grid[row][col].setBorder(BorderFactory.createLineBorder(Color.BLACK)); gridPanel.add(grid[row][col]); } } // Button panel with "Solve" button JPanel buttonPanel = new JPanel(); JButton solveButton = new JButton("Solve"); solveButton.setFont(new Font("Arial", Font.BOLD, 16)); solveButton.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { solveSudoku(); } }); buttonPanel.add(solveButton); // Add panels to the frame add(gridPanel, BorderLayout.CENTER); add(buttonPanel, BorderLayout.SOUTH); } // Parse the Sudoku grid from the UI into the board array private void parseInput() { for (int row = 0; row < SIZE; row++) { for (int col = 0; col < SIZE; col++) { String text = grid[row][col].getText(); if (text.isEmpty()) { board[row][col] = 0; // Empty cells are represented as 0 } else { board[row][col] = Integer.parseInt(text); } } } } // Display the solved Sudoku on the UI private void displaySolution() { for (int row = 0; row < SIZE; row++) { for (int col = 0; col < SIZE; col++) { grid[row][col].setText(String.valueOf(board[row][col])); } } } // Solve the Sudoku using the existing solver algorithm private void solveSudoku() { parseInput(); // Parse the UI input into the board array // Create an instance of the Sudoku solver with the current board SudokuOptimized solver = new SudokuOptimized(board); if (solver.solve()) { displaySolution(); // Display the solution on the UI JOptionPane.showMessageDialog(this, "Sudoku Solved!"); } else { JOptionPane.showMessageDialog(this, "Unsolvable Sudoku"); } } public static void main(String[] args) { // Create and display the Sudoku UI SwingUtilities.invokeLater(new Runnable() { @Override public void run() { SudokuUI sudokuUI = new SudokuUI(); sudokuUI.setVisible(true); } }); } 

}

class SudokuOptimized {

private int[][] board; public static final int EMPTY = 0; public static final int SIZE = 9; public SudokuOptimized(int[][] board) { this.board = board; } // Check if a number can be placed at a specific cell private boolean isSafe(int row, int col, int num) { int boxRowStart = row - row % 3; int boxColStart = col - col % 3; for (int i = 0; i < SIZE; i++) { if (board[row][i] == num || board[i][col] == num || board[boxRowStart + i / 3][boxColStart + i % 3] == num) { return false; } } return true; } // Find the next empty cell (used for backtracking) private int[] findNextEmptyCell() { for (int row = 0; row < SIZE; row++) { for (int col = 0; col < SIZE; col++) { if (board[row][col] == EMPTY) { return new int[] {row, col}; } } } return null; } // Solve the Sudoku using backtracking public boolean solve() { int[] emptyCell = findNextEmptyCell(); if (emptyCell == null) return true; // No empty cell, puzzle solved int row = emptyCell[0]; int col = emptyCell[1]; for (int num = 1; num <= SIZE; num++) { if (isSafe(row, col, num)) { board[row][col] = num; if (solve()) return true; board[row][col] = EMPTY; } } return false; } 

}
Output: