从无循环的映射类型和数组Scala中查找公共字符串

什么构成循环?

def common(arr: Array[String], m: Map[String,Int]): Array[Int] =
  arr flatMap m.get

common(Array("Ash","Garcia","Mac")
      ,Map("Ash" -> 5, "Mac" -> 4, "Lucas" -> 3))
// res0: Array[Int] = Array(5, 4)

yourArray.collect(yourMap) // Array(5,4) 

使用 .filter 若要仅查找匹配条目,请获取过滤映射的值。

鉴于

scala> val names = Array("Ash","Garcia","Mac")
names: Array[String] = Array(Ash, Garcia, Mac)

scala> val nameToNumber = Map("Ash" -> 5, "Mac" -> 4, "Lucas" -> 3)
nameToNumber: scala.collection.immutable.Map[String,Int] = Map(Ash -> 5, Mac -> 4, Lucas -> 3)

.filter.map

scala> nameToNumber.filter(x => names.contains(x._1)).map(_._2)
res3: scala.collection.immutable.Iterable[Int] = List(5, 4)

或者, you can use collect ,

scala> nameToNumber.collect{case kv if names.contains(kv._1) => kv._2}
res6: scala.collection.immutable.Iterable[Int] = List(5, 4)

你的复杂性在于 O(n2)

val a = Array("Ash","Garcia","Mac")
val m = Map("Ash" -> 5, "Mac" -> 4, "Lucas" -> 3)
println(m.filter { case (k, v) => a.contains(k)}.map { case (k, v) => v}.toArray)

这是解决方案