public/subjects/java/checkpoints/valid-sudoku/README.md

Valid Sudoku

Instructions

Determine if a 9x9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:

1. Each row must contain the digits 1-9 without repetition.
2. Each column must contain the digits 1-9 without repetition.
3. Each of the nine 3x3 sub-boxes of the grid must contain the digits 1-9 without repetition.

The Sudoku board could be partially filled, where empty cells are filled with the character '.'.

Expected Class

public class ValidSudoku {
    public boolean isValidSudoku(char[][] board) {
        // Implementation to determine if the Sudoku board is valid
    }
}

Usage

Here is a possible ExerciseRunner.java to test your class:

public class ExerciseRunner {
    public static void main(String[] args) {
        ValidSudoku validSudoku = new ValidSudoku();

        // Test case 1
        char[][] board1 = {
            {'5', '3', '.', '.', '7', '.', '.', '.', '.'},
            {'6', '.', '.', '1', '9', '5', '.', '.', '.'},
            {'.', '9', '8', '.', '.', '.', '.', '6', '.'},
            {'8', '.', '.', '.', '6', '.', '.', '.', '3'},
            {'4', '.', '.', '8', '.', '3', '.', '.', '1'},
            {'7', '.', '.', '.', '2', '.', '.', '.', '6'},
            {'.', '6', '.', '.', '.', '.', '2', '8', '.'},
            {'.', '.', '.', '4', '1', '9', '.', '.', '5'},
            {'.', '.', '.', '.', '8', '.', '.', '7', '9'}
        };
        System.out.println("Is board1 valid? " + validSudoku.isValidSudoku(board1)); // Expected output: true

        // Test case 2
        char[][] board2 = {
            {'8', '3', '.', '.', '7', '.', '.', '.', '.'},
            {'6', '.', '.', '1', '9', '5', '.', '.', '.'},
            {'.', '9', '8', '.', '.', '.', '.', '6', '.'},
            {'8', '.', '.', '.', '6', '.', '.', '.', '3'},
            {'4', '.', '.', '8', '.', '3', '.', '.', '1'},
            {'7', '.', '.', '.', '2', '.', '.', '.', '6'},
            {'.', '6', '.', '.', '.', '.', '2', '8', '.'},
            {'.', '.', '.', '4', '1', '9', '.', '.', '5'},
            {'.', '.', '.', '.', '8', '.', '.', '7', '9'}
        };
        System.out.println("Is board2 valid? " + validSudoku.isValidSudoku(board2)); // Expected output: false
    }
}

Expected Output

$ javac *.java -d build
$ java -cp build ExerciseRunner
Is board1 valid? true
Is board2 valid? false
$