Question

我有一个看起来像这样的scala multimap

Key: fish value: Set:(salmon,batam fish, shark)
Key: winged animals value: Set:(chicken, ducks)

我有一个字符串文本，如下所示：

val string = "the market had sold salmon and chicken"

由于这根绳子里有鲑鱼和鸡肉，我需要把钥匙放回鱼和有翅膀的动物身上。

有没有办法迭代值集并在匹配时返回密钥？我可以循环键值对，但我只能获得如上所示的多图，而不是单个值。

由于

Answer 1

val index: Map[String, Set[String]] = Map(
  "Fish" -> Set("salmon", "batam", "shark"),
  "Winged Animals" -> Set("chicken", "ducks"),
  "Other" -> Set("cow", "pig")
)

def typesInString(search: String): Set[String] = index.filter {
  case (t, vals) =>
    vals.exists(search.contains)
}.keys.toSet

typesInString("the market had sold salmon and chicken")
// Set(Fish, Winged Animals)

Answer 2

一种方法是从MultiMap创建反向Map以进行值键查找，如下所示：

import collection.mutable.{ Set, HashMap, MultiMap }

val text = "the market had sold salmon and chicken"

val mm = new HashMap[String, Set[String]] with MultiMap[String, String]

mm.addBinding("fish", "salmon")
mm.addBinding("fish", "batam fish")
mm.addBinding("fish", "shark")
mm.addBinding("winged animals", "chicken")
mm.addBinding("winged animals", "ducks")

val reverseList = for {
  mList <- mm.toList
  mValue <- mList._2
}
yield (mValue, mList._1)

// Use groupBy instead of toMap (*)
val reverseMap = reverseList.groupBy(_._1).mapValues(_.map(_._2))
// reverseMap: scala.collection.immutable.Map[String,List[String]] = Map(
//   salmon -> List(fish), ducks -> List(winged animals), chicken -> List(winged animals),
//   shark -> List(fish), batam fish -> List(fish)
// )

text.split("\\s+").collect{
  case x if reverseMap.contains(x) => reverseMap(x)
}
// res1: Array[List[String]] = Array(List(fish), List(winged animals))

（*）请注意，groupBy代替toMap会应用于reverseList，以允许属于多个群组的动物;这也是为什么结果是嵌套的集合（例如蝙蝠可能属于List（哺乳动物，有翼动物））。

Answer 3

如果没有循环键值对，只使用自己的MultiMap方法，我们仍然需要遍历键：

val items: MultiMap[String, String] = ...

val string = "the market had sold salmon and chicken"

val matched = items.keys.filter(key => items.entryExists(key, string.contains(_)))

println(matched)
// Set(winged animals, fish)

循环遍历多图值

3 个答案: