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Proper divisors: Difference between revisions

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Proper divisors (view source)

Revision as of 21:29, 5 April 2018

286 bytes removed ,  6 years ago
1. Shorter, 2. Supports numbers of any length, as long as you have enough ram, if someone wants to use Longs they can just replace every `BigInt` with a `Long` (and `BigInt(1)` with `1L`, additionally: 3. updated to latest Sala
(1. Shorter, 2. Supports numbers of any length, as long as you have enough ram, if someone wants to use Longs they can just replace every `BigInt` with a `Long` (and `BigInt(1)` with `1L`, additionally: 3. updated to latest Sala)
Line 3,762:
 
===Proper divisors for big (long) numbers===
<lang Scala>import scala.annotation.tailrec
import collection.parallel.mutable.ParSeq
 
def factorize(nx: LongBigInt): List[LongBigInt] = {
@tailrec
def factorsfoo(tuplex: (LongBigInt, Longa: BigInt = 2, list: List[LongBigInt], Int)= Nil): List[LongBigInt] = a * a > x match {
case false if x % a == 0 => foo(x / a, a, a :: list)
tuple match {
case false => foo(x, a + 1, list)
case (1, _, acc, _) => acc
case true => x :: list
case (n, k, acc, _) if (n % k == 0) => factors((n / k, k, acc ++ ParSeq(k), Math.sqrt(n / k).toInt))
}▼
case (n, k, acc, sqr) if (k < sqr) => factors(n, k + 1, acc, sqr)
 
case (n, k, acc, sqr) if (k >= sqr) => factors((1, k, acc ++ ParSeq(n), 0))
}foo(x)
▲ }
factors((n, 2, List[Long](), Math.sqrt(n).toInt))
}
 
def properDivisors(n: LongBigInt): List[BigInt] = {
val factors = factorize(n)
val products = (1 until factors.length).map(i =>
val products = (1 until factors.length).flatMap(i => factors.combinations(i).map(_.product).toList).flattentoList
(1LBigInt(1) +:: products).filter(_ < n)
}</lang>
 
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