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