Problem 3 updated

p03.scala

@@ -1,10 +1,7 @@
-lazy val ps: Stream[Int] = 2 #:: Stream.from(3).filter(i =>
-  ps.takeWhile(j => j * j <= i).forall(i % _ > 0))
+def factors(n: Long): List[Long] =
+  (2 to math.sqrt(n).toInt).find(n % _ == 0)
+    .map(i => i.toLong :: factors(n / i)).getOrElse(List(n))
 
-val n = 600851475143L
+val r = factors(600851475143L).last
 
-val limit = math.sqrt(n)
-
-val r = ps.view.takeWhile(_ < limit).filter(n % _ == 0).last
-
-assert(r == 6857) // 265 ms
+assert(r == 6857) // 1 ms