// ------------------------------------------------------------
// A small program showing how to remove every Nth element from
// a list using clear, expressive Kotlin patterns.
// ------------------------------------------------------------
/*
The function below returns a new list with every Nth element removed.
It uses `mapIndexed` to pair each element with its index, and then
filters based on the index. Kotlin's collection operators make this
both concise and easy to read.
Because indices start at 0, we check (index + 1) % n != 0 to keep
elements that are *not* in the Nth position.
*/
fun <T> removeEveryNth(items: List<T>, n: Int): List<T> {
require(n > 0) { "n must be a positive integer" }
return items
.mapIndexed { index, item -> index to item }
.filter { (index, _) -> (index + 1) % n != 0 }
.map { (_, item) -> item }
}
/*
Keeping main focused and readable makes the program easy to extend.
Here we demonstrate the function with a simple example.
*/
fun main() {
val data = (1..20).toList() // Example list: numbers 1–20
val n = 3 // Remove every 3rd element
val cleaned = removeEveryNth(data, n)
println("Original: $data")
println("After removing every $n-th element: $cleaned")
}
/*
run:
Original: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
After removing every 3-th element: [1, 2, 4, 5, 7, 8, 10, 11, 13, 14, 16, 17, 19, 20]
*/
