36 lines
1.3 KiB
Scala
36 lines
1.3 KiB
Scala
import spire.math.SafeLong
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import scala.annotation.tailrec
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import scala.collection.parallel.immutable.ParVector
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object SelfReferentialSequence {
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def main(args: Array[String]): Unit = {
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val nums = ParVector.range(1, 1000001).map(SafeLong(_))
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val seqs = nums.map{ n => val seq = genSeq(n); (n, seq, seq.length) }.toVector.sortWith((a, b) => a._3 > b._3)
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val maxes = seqs.takeWhile(t => t._3 == seqs.head._3)
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println(s"Seeds: ${maxes.map(_._1).mkString(", ")}\nIterations: ${maxes.head._3}")
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for(e <- maxes.distinctBy(a => nextTerm(a._1.toString))){
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println(s"\nSeed: ${e._1}\n${e._2.mkString("\n")}")
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}
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}
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def genSeq(seed: SafeLong): Vector[String] = {
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@tailrec
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def gTrec(seq: Vector[String], n: String): Vector[String] = {
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if(seq.contains(n)) seq
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else gTrec(seq :+ n, nextTerm(n))
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}
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gTrec(Vector[String](), seed.toString)
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}
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def nextTerm(num: String): String = {
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@tailrec
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def dTrec(digits: Vector[(Int, Int)], src: String): String = src.headOption match{
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case Some(n) => dTrec(digits :+ ((n.asDigit, src.count(_ == n))), src.filter(_ != n))
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case None => digits.sortWith((a, b) => a._1 > b._1).map(p => p._2.toString + p._1.toString).mkString
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}
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dTrec(Vector[(Int, Int)](), num)
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}
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}
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