集合的增量（多次通过）过滤的理想集合是什么？

Question

我看到了很多关于 Scala 集合的问题，但无法做出决定。 这个question 是迄今为止最有用的。

我认为问题的核心是双重的： 1）对于这个用例，哪些是最好的集合？ 2) 有哪些推荐的使用方式？

详情：

我正在实现一个迭代集合中所有元素的算法 搜索符合某个标准的那个。 搜索后，下一步是使用新标准再次搜索，但在可能性中没有选择的元素。 这个想法是创建一个序列，其中包含按标准排序的所有原始元素（在每次新选择时都会改变）。 原始序列实际上不需要排序，但可以有重复（算法一次只会选择一个）。 带有小整数序列的示例（只是为了简化）：

object Foo extends App {
  def f(already_selected: Seq[Int])(element: Int): Double =
  // something more complex happens here,
  // specially something take takes 'already_selected' into account
  math.sqrt(element)

  //call to the algorithm

  val (result, ti) = Tempo.time(recur(Seq.fill(9900)(Random.nextInt), Seq()))
  println("ti = " + ti)

  //algorithm
  def recur(collection: Seq[Int], already_selected: Seq[Int]): (Seq[Int], Seq[Int]) =
     if (collection.isEmpty) (Seq(), already_selected)
     else {
        val selected = collection maxBy f(already_selected)
        val rest = collection diff Seq(selected) //this part doesn't seem to be efficient
        recur(rest, selected +: already_selected)
     }
}

object Tempo {
 def time[T](f: => T): (T, Double) = {
    val s = System.currentTimeMillis
    (f, (System.currentTimeMillis - s) / 1000d)
 }
}

Answer 1

试试@inline 和 icn 建议的How can I idiomatically "remove" a single element from a list in Scala and close the gap?：

object Foo extends App {
  @inline
  def f(already_selected: Seq[Int])(element: Int): Double =
  // something more complex happens here,
  // specially something take takes 'already_selected' into account
    math.sqrt(element)

  //call to the algorithm

  val (result, ti) = Tempo.time(recur(Seq.fill(9900)(Random.nextInt()).zipWithIndex, Seq()))
  println("ti = " + ti)

  //algorithm
  @tailrec
  def recur(collection: Seq[(Int, Int)], already_selected: Seq[Int]): Seq[Int] =
    if (collection.isEmpty) already_selected
    else {
      val (selected, i) = collection.maxBy(x => f(already_selected)(x._2))
      val rest = collection.patch(i, Nil, 1) //this part doesn't seem to be efficient
      recur(rest, selected +: already_selected)
    }
}

object Tempo {
  def time[T](f: => T): (T, Double) = {
    val s = System.currentTimeMillis
    (f, (System.currentTimeMillis - s) / 1000d)
  }
}