Question

以函数/ Scala方式查找每个元素出现次数的最佳方法是什么？

Seq(Set("a", "b", "c"), Set("b"), Set("b", "c"))

因此，我需要像

这样的东西

Set(("a", 1), ("b", 3), ("c", 2))

谢谢！

Answer 1

使用flatten和groupBy：

scala> val s = Seq(Set("a", "b", "c"), Set("b"), Set("b", "c"))
s: Seq[scala.collection.immutable.Set[String]] =
  List(Set(a, b, c), Set(b), Set(b, c))

scala> s.flatten
res0: Seq[String] =
  List(a, b, c, b, b, c)

scala> s.flatten.groupBy(identity)
res3: scala.collection.immutable.Map[String,Seq[String]] =
  Map(b -> List(b, b, b), a -> List(a), c -> List(c, c))

scala> s.flatten.groupBy(identity).map { case (k, v) => (k, v.size) }.toSet
res7: scala.collection.immutable.Set[(String, Int)] =
  Set((b,3), (a,1), (c,2))

Answer 2

scala> val x = Seq(Set("a", "b", "c"), Set("b"), Set("b", "c"))
x: Seq[scala.collection.immutable.Set[String]] = List(Set(a, b, c), Set(b), Set(b, c))
scala> (x.flatten groupBy identity mapValues (_.size)).toSet
res3: scala.collection.immutable.Set[(String, Int)] = Set((b,3), (a,1), (c,2))

以功能方式查找内部集合中的多个事件

2 个答案: