比较 Scala 列表中元素的索引

Question

我有 2 个列表

val listA = List("Mary", "Harry", "Marry", "Harry", "Marry")
val listB = List("Mary", "Harry", "Marry", "Harry", "Marry")

现在我想知道两个列表中所有出现的Harry的索引是否相同。在 scala 中最好的方法是什么？

Answer 1

我会使用迭代器只在需要的时候进行比较，就像这样：

def indexesOf(ls: List[String], word: String) =
  ls.iterator.zipWithIndex.collect { case (`word`, i) => i }

indexesOf(listA, "Harry") sameElements indexesOf(listB, "Harry")

Answer 2

您可以 .zip 将列表放在一起，然后使用 .exists 检查是否存在一个元组，其中一个等于 "Harry" 而另一个不等于：

scala> val listA = List("Mary", "Harry", "Marry", "Harry", "Marry")
listA: List[String] = List(Mary, Harry, Marry, Harry, Marry)

scala> val listB = List("Mary", "Harry", "Marry", "Harry", "Marry")
listB: List[String] = List(Mary, Harry, Marry, Harry, Marry)

scala> (listA zip listB).exists { case (a, b) => (a == "Harry" ^ b == "Harry") }
res5: Boolean = false

scala> val listA = List("Mary", "Harry", "Marry", "Harry", "Marry")
listA: List[String] = List(Mary, Harry, Marry, Harry, Marry)

scala> val listB = List("Mary", "Harry", "Marry", "Harry", "Harry") // changed the last one
listB: List[String] = List(Mary, Harry, Marry, Harry, Harry)

scala> (listA zip listB).exists { case (a, b) => (a == "Harry" ^ b == "Harry") }
res6: Boolean = true

比较 Scala 列表中元素的索引

comparing the index of element in scala list

scala

scala-collections