// Sudoku solution must satisfy all of the following rules:
// Each of the digits 1-9 must occur once in each row.
// Each of the digits 1-9 must occur once in each column.
// Each of the digits 1-9 must occur once in each 3x3 grid.
function isValidSudoku3x3Grid($grid) {
if (count($grid) != 3 || count($grid[0]) != 3) {
return false; // Ensure it's a 3x3 grid
}
$seen = [];
foreach ($grid as $row) {
foreach ($row as $num) {
if ($num < 1 || $num > 9 || in_array($num, $seen)) {
return false; // Invalid if number is out of range or repeated
}
$seen[] = $num;
}
}
return true; // Valid if all numbers 1-9 appear exactly once
}
$grid = [
[5, 3, 4],
[6, 7, 2],
[1, 9, 8]
];
if (isValidSudoku3x3Grid($grid)) {
echo "The grid is a valid Sudoku grid!\n";
} else {
echo "The grid is NOT a valid Sudoku grid!\n";
}
/*
run:
The grid is a valid Sudoku grid!
*/
