Question

我有一张地图，并使用

在地图中添加索引

val indexByColName = sorted.view.zipWithIndex.toMap

如何找到特定密钥的索引？

Answer 1

定义sorted并显示您想要的输出会有所帮助，但我认为这可能会有所帮助。

scala> val sorted = Map("zero" -> 0, "one" -> 1, "two" -> 2)
sorted: scala.collection.immutable.Map[String,Int] = Map(zero -> 0, one -> 1, two -> 2)

scala> val indexByColName =sorted.view.zipWithIndex.toMap
indexByColName: scala.collection.immutable.Map[(String, Int),Int] = Map((zero,0) -> 0, (one,1) -> 1, (two,2) -> 2)

scala> indexByColName.get(("zero", 0)).get
res1: Int = 0

scala> indexByColName.get(("two", 2)).get

res3: Int = 2

Answer 2

indexWhere中的方法Array提供了如下语义，

implicit class keyIndexing[A,B](val m: Map[A,B]) extends AnyVal {
  def keyIndex(key: A, value: B) = {
    m.toArray.indexWhere{ case (k,v) => key == k && value == v }
  }
}

然后

val sorted = Map("a" -> 10, "b" -> 11, "c" -> 12)

scala> sorted.keyIndex("a",10)
res15: Int = 0

和非匹配（或非现有）键和值

scala> sorted.keyIndex("a",11)
res16: Int = -1

scala> sorted.keyIndex("z",11)
res19: Int = -1

如何在地图中找到关键索引？

2 个答案: