Java GUI Sudoku Solver

This is a Java-based Graphical User Interface (GUI) Sudoku Solver. It provides an interactive interface for solving Sudoku puzzles. It is written in Java and uses a backtracking algorithm to solve the puzzle.

Documentation

• A user-friendly GUI that allows input of the Sudoku puzzle.
• The ability to solve any valid Sudoku puzzle.
• Provides a clear message if the puzzle is unsolvable.
• The ability to save and load puzzles from a file.
• Support for different levels of difficulty.

Admin Password

Username : admin1 Password : admin123

Algorithm

SudokuSolver Class

acbd1dc3025ed61b0c93d0cb2c18929ee49990ee The Backtracking Algorithm is implemented in the SudokuSolver.java. It's implemented in the private solve method.

The algorithm starts at line 29:

private static boolean solve(int[][] puzzle, int row, int col) {

First, it checks if we've reached the end of the puzzle:

if (row == 9) {
    // All rows have been filled, and the puzzle is solved
    return true;
}

If we've reached the end of a row, it moves to the next row:

if (col == 9) {
    // Move to the next row
    return solve(puzzle, row + 1, 0);
}

If the current cell is already filled, it moves to the next cell:

if (puzzle[row][col] != 0) {
    // Cell is already filled, move to next cell
    return solve(puzzle, row, col + 1);
}

The core of the algorithm is in the following loop:

for (int value = 1; value <= 9; value++) {
    if (isValid(puzzle, row, col, value)) {
        puzzle[row][col] = value;
        if (solve(puzzle, row, col + 1)) {
            return true;
        }
        puzzle[row][col] = 0; // Backtrack
    }
}

This loop tries each value from 1 to 9 in the current cell. If a value is valid (doesn't violate Sudoku rules), it:

• Places the value in the cell
• Recursively tries to solve the rest of the puzzle
• If the recursive call returns true, it means a solution is found
• If not, it backtracks by setting the cell back to 0 and tries the next value

If no value works for this cell, it returns false, which triggers backtracking in the previous recursive call:

return false;

The isValid method (lines 64-82) checks if placing a value in a specific cell violates any Sudoku rules by checking the row, column, and 3x3 sub-grid.

SudokuGenerator Class

Another part is SudokuGenerator.java which contains an algorithm for generating Sudoku puzzles. The core of the generation algorithm is contained in the solve method, which uses a recursive backtracking approach to generate a complete Sudoku solution.

The algorithm starts at line 76:

private boolean solve(int row, int col) {
    if (col == 9) {
        col = 0;
        row++;
        if (row == 9) {
            return true;
        }
    }

This part handles moving to the next row when we reach the end of a column. If we've filled the entire grid (row == 9), we return true as we've found a solution.

if (solution[row][col] != 0) {
        return solve(row, col + 1);
    }

If the current cell is already filled (not 0), we move to the next cell.

List<Integer> numbers = generateRandomNumbers();
    for (int num : numbers) {
        if (isSafe(row, col, num)) {
            solution[row][col] = num;
            if (solve(row, col + 1)) {
                return true;
            }
            solution[row][col] = 0;
        }
    }

This is the core of the backtracking algorithm:

• We generate a list of numbers 1-9 in random order.
• For each number, we check if it's safe to place in the current cell.
• If it's safe, we place the number and recursively try to solve the rest of the grid.
• If the recursive call returns true, we've found a solution.
• If not, we remove the number (backtrack) and try the next number.

return false;

If we've tried all numbers and none work, we return false to trigger backtracking.

The isSafe method (lines 157-159) checks if a number can be placed in a cell without violating Sudoku rules:

private boolean isSafe(int row, int col, int num) {
    return !usedInRow(row, num) && !usedInColumn(col, num) && !usedInBox(row - row % 3, col - col % 3, num);
}

After generating a complete solution, the algorithm removes cells to create the puzzle:

private void removeCells(int difficulty) {
    Random rand = new Random();
    int cellsToRemove = 81 - difficulty;

    while (cellsToRemove > 0) {
        int row = rand.nextInt(9);
        int col = rand.nextInt(9);

        if (puzzle[row][col] != 0) {
            int temp = puzzle[row][col];
            puzzle[row][col] = 0;

            if (!hasUniqueSolution()) {
                puzzle[row][col] = temp;
            } else {
                cellsToRemove--;
            }
        }
    }
}

This method:

• Randomly selects cells to remove.
• Removes a cell's value temporarily.
• Check if the puzzle still has a unique solution.
• If not, it restores the value; if yes, it keeps the cell empty.
• Continues until the desired number of cells are removed.

Features

• A user-friendly GUI that allows input of the Sudoku puzzle.
• The ability to solve any valid Sudoku puzzle.
• Provides a clear message if the puzzle is unsolvable.
• The ability to save and load puzzles from a file.
• Support for different levels of difficulty.

Installation

<<<<<<< HEAD

• Clone or download the project from GitHub.
• Open the project in your preferred Java Integrated Development Environment (IDE).
• Add jar files to the classpath if needed.
• Create the database using the provided SQL file.
• Build and run the project from your IDE.

Usage

• Run the project.
• Login or Register as a user.
• Enter the values in the empty cells of the Sudoku puzzle in the GUI.
• Click on the "Solve" button to solve the puzzle.
• If the puzzle is solvable, the solved puzzle will be displayed in the GUI.
• A clear message will be displayed in the GUI if the puzzle is unsolvable or has multiple solutions. =======
• Clone or download the project from GitHub.
• Open the project in your preferred Java Integrated Development Environment (IDE).
• Add jar files to the classpath if needed.
• Create the database using the provided SQL file.
• Build and run the project from your IDE.

Run Locally

• Run the project.
• Login or Register as a user.
• Enter the values in the empty cells of the Sudoku puzzle in the GUI.
• Click on the "Solve" button to solve the puzzle.
• If the puzzle is solvable, the solved puzzle will be displayed in the GUI.
• A clear message will be displayed in the GUI if the puzzle is unsolvable or has multiple solutions.

acbd1dc3025ed61b0c93d0cb2c18929ee49990ee

Future Enhancements

<<<<<<< HEAD

• Improve the algorithm to make it more efficient and faster
• Add a feature to allow users to highlight cells that contain the same value =======
• Improve the algorithm to make it more efficient and faster
• Add a feature to allow users to highlight cells that contain the same value

License

MIT

acbd1dc3025ed61b0c93d0cb2c18929ee49990ee