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November 18, 2022 07:50
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php matrix determinant
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<?php | |
$matrix = [ | |
1, 1, 1, 1, | |
4, 3, 2, 1, | |
2, 3, 4, 1, | |
3, 4, 3, 1 | |
]; | |
require 'Matrix.php'; | |
$matrix = (new Matrix(4, 4))->load($matrix); | |
echo $matrix->det(); |
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<?php | |
class Matrix | |
{ | |
private $rows = 0; | |
private $cols = 0; | |
private $data = null; | |
public function __construct($rows, $cols) | |
{ | |
$this->rows = $rows; | |
$this->cols = $cols; | |
} | |
public function load($data) | |
{ | |
if (count($data) === $this->rows * $this->cols) { | |
$this->data = $data; | |
} | |
else { | |
$this->rows = 0; | |
$this->cols = 0; | |
} | |
return $this; | |
} | |
public function getLinearIndex($i, $j) | |
{ | |
return $this->cols * $i + $j; | |
} | |
public function get($i, $j) | |
{ | |
$index = $this->getLinearIndex($i, $j); | |
return isset($this->data[$index]) ? $this->data[$index] : null; | |
} | |
public function getAlgebraicExtension($ci, $cj) | |
{ | |
$matrix = []; | |
for ($i = 0; $i < $this->rows; $i++) { | |
if ($i === $ci) continue; | |
for ($j = 0; $j < $this->cols; $j++) { | |
if ($j === $cj) continue; | |
$matrix[] = $this->get($i, $j); | |
} | |
} | |
return $matrix; | |
} | |
public function det() | |
{ | |
$s = 0; | |
if ($this->rows === 2 && $this->cols === 2) { | |
return $this->get(0, 0) * $this->get(1, 1) - $this->get(1, 0) * $this->get(0, 1); | |
} | |
for ($j = 0; $j < $this->cols; $j++) { | |
$matrix = (new Matrix($this->rows - 1, $this->cols - 1))->load($this->getAlgebraicExtension(0, $j)); | |
$s += $this->get(0, $j) * pow(-1, $j) * $matrix->det(); | |
} | |
return $s; | |
} | |
} |
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