Improve performance of TimeEfficientLongestCommonSubsequenceCalculator

Author: staabm

src/TimeEfficientLongestCommonSubsequenceCalculator.php

@@ -37,12 +37,24 @@ public function calculate(array $from, array $to): array
 
         for ($i = 1; $i <= $fromLength; $i++) {
             for ($j = 1; $j <= $toLength; $j++) {
-                $o          = ($j * $width) + $i;
-                $matrix[$o] = max(
-                    $matrix[$o - 1],
-                    $matrix[$o - $width],
-                    $from[$i - 1] === $to[$j - 1] ? $matrix[$o - $width - 1] + 1 : 0
-                );
+                $o = ($j * $width) + $i;
+
+                // don't use max() to avoid function call overhead
+                $firstOrLast = $from[$i - 1] === $to[$j - 1] ? $matrix[$o - $width - 1] + 1 : 0;
+
+                if ($matrix[$o - 1] > $matrix[$o - $width]) {
+                    if ($firstOrLast > $matrix[$o - 1]) {
+                        $matrix[$o] = $firstOrLast;
+                    } else {
+                        $matrix[$o] = $matrix[$o - 1];
+                    }
+                } else {
+                    if ($firstOrLast > $matrix[$o - $width]) {
+                        $matrix[$o] = $firstOrLast;
+                    } else {
+                        $matrix[$o] = $matrix[$o - $width];
+                    }
+                }
             }
         }