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Ingy döt Net 2023-07-01 11:58:00 -04:00
parent 7387c8f97b
commit cb5bb5e222
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Task/Successive-prime-differences/Scala/successive-prime-differences.scala Normal file
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object SuccessivePrimeDiffs {
def main(args: Array[String]): Unit = {
val d2 = primesByDiffs(2)(1000000)
val d1 = primesByDiffs(1)(1000000)
val d22 = primesByDiffs(2, 2)(1000000)
val d24 = primesByDiffs(2, 4)(1000000)
val d42 = primesByDiffs(4, 2)(1000000)
val d642 = primesByDiffs(6, 4, 2)(1000000)
if(true) println(
s"""|Diffs: (First), (Last), Count
|2: (${d2.head.mkString(", ")}), (${d2.last.mkString(", ")}), ${d2.size}
|1: (${d1.head.mkString(", ")}), (${d1.last.mkString(", ")}), ${d1.size}
|2-2: (${d22.head.mkString(", ")}), (${d22.last.mkString(", ")}), ${d22.size}
|2-4: (${d24.head.mkString(", ")}), (${d24.last.mkString(", ")}), ${d24.size}
|4-2: (${d42.head.mkString(", ")}), (${d42.last.mkString(", ")}), ${d42.size}
|6-4-2: (${d642.head.mkString(", ")}), (${d642.last.mkString(", ")}), ${d642.size}
|""".stripMargin)
}
def primesByDiffs(diffs: Int*)(max: Int): LazyList[Vector[Int]] = {
primesSliding(diffs.size + 1)
.takeWhile(_.last <= max)
.filter{vec => diffs.zip(vec.init).map{case (a, b) => a + b} == vec.tail}
.to(LazyList)
}
def primesSliding(len: Int): Iterator[Vector[Int]] = primes.sliding(len).map(_.toVector)
def primes: LazyList[Int] = 2 #:: LazyList.from(3, 2).filter(n => !Iterator.range(3, math.sqrt(n).toInt + 1, 2).exists(n%_ == 0))
}