Add cache improvements

Maths/Factorial.php

@@ -10,11 +10,21 @@
  */
 function factorial(int $number)
 {
+    static $cache = [];//internal caching memory for speed
+
     if ($number < 0) {
         throw new \Exception("Negative numbers are not allowed for calculating Factorial");
     }
     if ($number === 0) {
         return 1; // Factorial of 0 is 1
     }
-    return ($number * factorial($number - 1)); // Recursion since x! = x * (x-1)!
+    
+    if (isset($cache[$number])) {
+        return $cache[$number];
+    }
+
+    $fact = ($number * factorial($number - 1)); // Recursion since x! = x * (x-1)!
+    $cache[$number] = $fact;
+
+    return $fact;
 }