Question

How to rotate a matrix 90 degrees clockwise in PHP

Answer 1

function rotate90Clockwise(&$matrix) {
    $rows = count($matrix); // Number of rows
    
    // Step 1: Transpose the matrix
    for ($i = 0; $i < $rows; $i++) {
        for ($j = $i; $j < $rows; $j++) {
            $temp = $matrix[$i][$j];
            $matrix[$i][$j] = $matrix[$j][$i];
            $matrix[$j][$i] = $temp;
        }
    }
 
    // Step 2: Reverse each row
    for ($i = 0; $i < $rows; $i++) {
        $matrix[$i] = array_reverse($matrix[$i]);
    }
}
 
function printMatrix($matrix) {
    foreach ($matrix as $row) {
        echo implode(" ", $row) . PHP_EOL;
    }
}
 
$matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
];
 
echo "Original Matrix:\n";
printMatrix($matrix);
 
rotate90Clockwise($matrix);
 
echo "\nRotated Matrix:\n";
printMatrix($matrix);
 
 
  
/*
run:
  
Original Matrix:
1 2 3
4 5 6
7 8 9

Rotated Matrix:
7 4 1
8 5 2
9 6 3
 
*/

 

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Answer 2

function rotate90Clockwise($matrix) {
    $rows = count($matrix); // Number of rows
    $cols = count($matrix[0]); // Number of columns
    
    $rotated = array_fill(0, $cols, array_fill(0, $rows, 0));

    for ($i = 0; $i < $rows; $i++) {
        for ($j = 0; $j < $cols; $j++) {
            $rotated[$j][$rows - 1 - $i] = $matrix[$i][$j]; // Mapping to rotated position
        }
    }
    return $rotated;
}

function printMatrix($matrix) {
    foreach ($matrix as $row) {
        echo implode(" ", $row) . PHP_EOL;
    }
}

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

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

$rotated = rotate90Clockwise($matrix);

echo "\nRotated Matrix:\n";
printMatrix($rotated);


 
/*
run:
 
Original Matrix:
1 2 3 4
5 6 7 8
9 10 11 12

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

*/

 

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