Chris@0: <?php
Chris@0: /*
Chris@12:  * This file is part of sebastian/diff.
Chris@0:  *
Chris@0:  * (c) Sebastian Bergmann <sebastian@phpunit.de>
Chris@0:  *
Chris@0:  * For the full copyright and license information, please view the LICENSE
Chris@0:  * file that was distributed with this source code.
Chris@0:  */
Chris@0: 
Chris@0: namespace SebastianBergmann\Diff\LCS;
Chris@0: 
Chris@0: /**
Chris@0:  * Time-efficient implementation of longest common subsequence calculation.
Chris@0:  */
Chris@0: class TimeEfficientImplementation implements LongestCommonSubsequence
Chris@0: {
Chris@0:     /**
Chris@0:      * Calculates the longest common subsequence of two arrays.
Chris@0:      *
Chris@0:      * @param array $from
Chris@0:      * @param array $to
Chris@0:      *
Chris@0:      * @return array
Chris@0:      */
Chris@0:     public function calculate(array $from, array $to)
Chris@0:     {
Chris@0:         $common     = array();
Chris@12:         $fromLength = \count($from);
Chris@12:         $toLength   = \count($to);
Chris@0:         $width      = $fromLength + 1;
Chris@0:         $matrix     = new \SplFixedArray($width * ($toLength + 1));
Chris@0: 
Chris@0:         for ($i = 0; $i <= $fromLength; ++$i) {
Chris@0:             $matrix[$i] = 0;
Chris@0:         }
Chris@0: 
Chris@0:         for ($j = 0; $j <= $toLength; ++$j) {
Chris@0:             $matrix[$j * $width] = 0;
Chris@0:         }
Chris@0: 
Chris@0:         for ($i = 1; $i <= $fromLength; ++$i) {
Chris@0:             for ($j = 1; $j <= $toLength; ++$j) {
Chris@0:                 $o          = ($j * $width) + $i;
Chris@12:                 $matrix[$o] = \max(
Chris@0:                     $matrix[$o - 1],
Chris@0:                     $matrix[$o - $width],
Chris@0:                     $from[$i - 1] === $to[$j - 1] ? $matrix[$o - $width - 1] + 1 : 0
Chris@0:                 );
Chris@0:             }
Chris@0:         }
Chris@0: 
Chris@0:         $i = $fromLength;
Chris@0:         $j = $toLength;
Chris@0: 
Chris@0:         while ($i > 0 && $j > 0) {
Chris@12:             if ($from[$i - 1] === $to[$j - 1]) {
Chris@12:                 $common[] = $from[$i - 1];
Chris@0:                 --$i;
Chris@0:                 --$j;
Chris@0:             } else {
Chris@0:                 $o = ($j * $width) + $i;
Chris@12: 
Chris@0:                 if ($matrix[$o - $width] > $matrix[$o - 1]) {
Chris@0:                     --$j;
Chris@0:                 } else {
Chris@0:                     --$i;
Chris@0:                 }
Chris@0:             }
Chris@0:         }
Chris@0: 
Chris@12:         return \array_reverse($common);
Chris@0:     }
Chris@0: }