Question

How to inverse N x M matrix in PHP

Answer 1

function printMatrix(array $matrix): void {
    $rows = count($matrix);              // number of rows
    $cols = count($matrix[0]);           // number of columns

    for ($i = 0; $i < $rows; $i++) {
        $row = '';
        for ($j = 0; $j < $cols; $j++) {
            // printf with width specifier for padding
            $row .= sprintf("%4d", $matrix[$i][$j]);
        }
        echo $row . PHP_EOL;
    }
}

function inverseMatrix(array &$matrix): void {
    $rows = count($matrix);
    $cols = count($matrix[0]);
    $counter = 0;

    for ($i = 0, $r = $rows - 1; $i < $rows; $i++, $r--) {
        for ($j = 0, $c = $cols - 1; $j < $cols; $j++, $c--) {
            // swap values
            $temp = $matrix[$i][$j];
            $matrix[$i][$j] = $matrix[$r][$c];
            $matrix[$r][$c] = $temp;

            $counter++;
            if ($counter > ($rows * $cols) / 2 - 1) {
                return;
            }
        }
    }
}

$matrix = [
    [1, 2, 3, 4],
    [5, 6, 7, 8],
    [9, 10, 11, 12]
];

echo "matrix:\n";
printMatrix($matrix);

inverseMatrix($matrix);

echo "\ninverse matrix:\n";
printMatrix($matrix);



/*
run:

matrix:
   1   2   3   4
   5   6   7   8
   9  10  11  12

inverse matrix:
  12  11  10   9
   8   7   6   5
   4   3   2   1

*/

 

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