Chris@14: <?php declare(strict_types=1);
Chris@14: /*
Chris@14:  * This file is part of sebastian/diff.
Chris@14:  *
Chris@14:  * (c) Sebastian Bergmann <sebastian@phpunit.de>
Chris@14:  *
Chris@14:  * For the full copyright and license information, please view the LICENSE
Chris@14:  * file that was distributed with this source code.
Chris@14:  */
Chris@14: 
Chris@14: namespace SebastianBergmann\Diff;
Chris@14: 
Chris@14: final class TimeEfficientLongestCommonSubsequenceCalculator implements LongestCommonSubsequenceCalculator
Chris@14: {
Chris@14:     /**
Chris@14:      * {@inheritdoc}
Chris@14:      */
Chris@14:     public function calculate(array $from, array $to): array
Chris@14:     {
Chris@14:         $common     = [];
Chris@14:         $fromLength = \count($from);
Chris@14:         $toLength   = \count($to);
Chris@14:         $width      = $fromLength + 1;
Chris@14:         $matrix     = new \SplFixedArray($width * ($toLength + 1));
Chris@14: 
Chris@14:         for ($i = 0; $i <= $fromLength; ++$i) {
Chris@14:             $matrix[$i] = 0;
Chris@14:         }
Chris@14: 
Chris@14:         for ($j = 0; $j <= $toLength; ++$j) {
Chris@14:             $matrix[$j * $width] = 0;
Chris@14:         }
Chris@14: 
Chris@14:         for ($i = 1; $i <= $fromLength; ++$i) {
Chris@14:             for ($j = 1; $j <= $toLength; ++$j) {
Chris@14:                 $o          = ($j * $width) + $i;
Chris@14:                 $matrix[$o] = \max(
Chris@14:                     $matrix[$o - 1],
Chris@14:                     $matrix[$o - $width],
Chris@14:                     $from[$i - 1] === $to[$j - 1] ? $matrix[$o - $width - 1] + 1 : 0
Chris@14:                 );
Chris@14:             }
Chris@14:         }
Chris@14: 
Chris@14:         $i = $fromLength;
Chris@14:         $j = $toLength;
Chris@14: 
Chris@14:         while ($i > 0 && $j > 0) {
Chris@14:             if ($from[$i - 1] === $to[$j - 1]) {
Chris@14:                 $common[] = $from[$i - 1];
Chris@14:                 --$i;
Chris@14:                 --$j;
Chris@14:             } else {
Chris@14:                 $o = ($j * $width) + $i;
Chris@14: 
Chris@14:                 if ($matrix[$o - $width] > $matrix[$o - 1]) {
Chris@14:                     --$j;
Chris@14:                 } else {
Chris@14:                     --$i;
Chris@14:                 }
Chris@14:             }
Chris@14:         }
Chris@14: 
Chris@14:         return \array_reverse($common);
Chris@14:     }
Chris@14: }