Odd squarefree semiprimes: Difference between revisions
→{{header|Scala}}
Line 1,127:
=={{header|Scala}}==
<syntaxhighlight lang="scala">
val primes3 = 3 #:: LazyList.from(5, 6)
.flatMap(p => Iterator(p, p + 2))
.filter(p => (5 to math.sqrt(p).floor.toInt by 6).forall(a => p % a > 0 && p % (a + 2) > 0))
def merge(sort1: Seq[Int], sort2: Seq[Int]): Seq[Int] = {
def iter(sort1: Seq[Int], sort2: Seq[Int], acc: Seq[Int]): Seq[Int] = {
if (sort1.isEmpty) return acc ++ sort2
val (x, y) = (sort1.head, sort2.head)
val (min, s1, s2) = if (x < y) (x, sort1.tail, sort2)
else (y, sort2.tail, sort1)
iter(s1, s2, acc :+ min)
}
iter(sort1, sort2, Seq())
}
def semiPrimes(limit: Int): Seq[Int] = { // odd and squarefree
def iter(primeList: Seq[Int], acc: Seq[Int]): Seq[Int] = {
val (start, primeList1) = (primeList.head, primeList.tail)
val subList = primeList1.map(_ * start).takeWhile(_ <= limit)
if (subList.isEmpty) return acc
iter(primeList1, merge(acc, subList))
}
iter(primes3, Seq()) //.sorted
}
@main def main = {
val start = System.currentTimeMillis
val spList = semiPrimes(1000)
val duration = System.currentTimeMillis - start
spList.grouped(20).foreach(group =>
group.foreach(sp => print(f"$sp%3d "))
println
)
println(s"number: ${spList.length} [time elapsed: $duration ms]")
}
</syntaxhighlight>
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