Kotlin filter lambda array using iteration index

问题

I would like to filter an array into an array of every nth item. For examples:

fun getNth(array: Array<Any>, n: Int): Array<Any> {
    val newList = ArrayList<Any>()
    for  (i in 0..array.size) {
        if (i % n == 0) {
            newList.add(array[i])
        }
    }
    return newList.toArray()
}

Is there an idiomatic way to do this using for example Kotlin's .filter() and without A) provisioning a new ArrayList and B) manually iterating with a for/in loop?

回答1:

filterIndexed function is suited exactly for this case:

array.filterIndexed { index, value -> index % n == 0 }

回答2:

Use Array.withIndex():

https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/with-index.html:

array.withIndex().filter { (i, value) -> i % n == 0 }.map { (i, value) -> value }

来源：https://stackoverflow.com/questions/46867406/kotlin-filter-lambda-array-using-iteration-index