comparison vendor/sebastian/diff/src/LCS/MemoryEfficientLongestCommonSubsequenceImplementation.php @ 0:4c8ae668cc8c

Initial import (non-working)

+<?php
+/*
+ * This file is part of the Diff package.
+ *
+ * (c) Sebastian Bergmann <[e-mail]>
+ *
+ * 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;
+    }
+}