'kotlin: what is the best way to determine if 2 lists have any common element?

What is the best way to find if 2 lists have at least one element in common? I am trying to do this in kotlin and while this is quite easy, I wanted to explore which is the best way to do this.

Problem:

fun isAnyElementCommon(
    alist: List<String>,
    blist: List<String>
):Boolean

one example would be:

= alist.intersect(blist).isNotEmpty()

but I think that is too much processing to find out all the common values and then checking if it is empty

EDIT

another would be:

= alist.any{ blist.contains(it) }

I am aware of these solutions. I just wanted to know if there are better ways to approach this problem. If not, then that is also fine. I am looking for a low complexity and low memory footprint solution. Also, in kotlin, most cases are covered by some helper extension functions. So maybe if there is anything like this. I would like to know.

listalgorithmperformancekotlinoptimization


Solution 1:[1]

To get it down to O(n), convert one list to a Set first.

fun isAnyElementCommon(
    aList: List<String>,
    bList: List<String>
):Boolean {
    val aSet = aList.toSet()
    return bList.any { it in aSet }
}

Solution 2:[2]

Maybe not Kotlin-esque enough, but Java's Collections.disjoint() is optimized for this:

fun isAnyElementCommon(
    alist: List<String>,
    blist: List<String>
):Boolean =
    !Collections.disjoint(aList, bList)

Solution 3:[3]

  1. Put one list into a hash map.
  2. Iterate over second list and return true if an element from second list is present in hash map.

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 Tenfour04
Solution 2 Ridcully
Solution 3 Shridhar R Kulkarni

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