94 lines
2.4 KiB
PHP
94 lines
2.4 KiB
PHP
<?php
|
|
/*
|
|
* This file is part of the Diff package.
|
|
*
|
|
* (c) Sebastian Bergmann <sebastian@phpunit.de>
|
|
*
|
|
* For the full copyright and license information, please view the LICENSE
|
|
* file that was distributed with this source code.
|
|
*/
|
|
|
|
namespace SebastianBergmann\Diff\LCS;
|
|
|
|
/**
|
|
* Memory-efficient implementation of longest common subsequence calculation.
|
|
*/
|
|
class MemoryEfficientImplementation implements LongestCommonSubsequence
|
|
{
|
|
/**
|
|
* Calculates the longest common subsequence of two arrays.
|
|
*
|
|
* @param array $from
|
|
* @param array $to
|
|
*
|
|
* @return array
|
|
*/
|
|
public function calculate(array $from, array $to)
|
|
{
|
|
$cFrom = count($from);
|
|
$cTo = count($to);
|
|
|
|
if ($cFrom == 0) {
|
|
return array();
|
|
} elseif ($cFrom == 1) {
|
|
if (in_array($from[0], $to)) {
|
|
return array($from[0]);
|
|
} else {
|
|
return array();
|
|
}
|
|
} else {
|
|
$i = intval($cFrom / 2);
|
|
$fromStart = array_slice($from, 0, $i);
|
|
$fromEnd = array_slice($from, $i);
|
|
$llB = $this->length($fromStart, $to);
|
|
$llE = $this->length(array_reverse($fromEnd), array_reverse($to));
|
|
$jMax = 0;
|
|
$max = 0;
|
|
|
|
for ($j = 0; $j <= $cTo; $j++) {
|
|
$m = $llB[$j] + $llE[$cTo - $j];
|
|
|
|
if ($m >= $max) {
|
|
$max = $m;
|
|
$jMax = $j;
|
|
}
|
|
}
|
|
|
|
$toStart = array_slice($to, 0, $jMax);
|
|
$toEnd = array_slice($to, $jMax);
|
|
|
|
return array_merge(
|
|
$this->calculate($fromStart, $toStart),
|
|
$this->calculate($fromEnd, $toEnd)
|
|
);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* @param array $from
|
|
* @param array $to
|
|
*
|
|
* @return array
|
|
*/
|
|
private function length(array $from, array $to)
|
|
{
|
|
$current = array_fill(0, count($to) + 1, 0);
|
|
$cFrom = count($from);
|
|
$cTo = count($to);
|
|
|
|
for ($i = 0; $i < $cFrom; $i++) {
|
|
$prev = $current;
|
|
|
|
for ($j = 0; $j < $cTo; $j++) {
|
|
if ($from[$i] == $to[$j]) {
|
|
$current[$j + 1] = $prev[$j] + 1;
|
|
} else {
|
|
$current[$j + 1] = max($current[$j], $prev[$j + 1]);
|
|
}
|
|
}
|
|
}
|
|
|
|
return $current;
|
|
}
|
|
}
|