that is better than repeated

removeLast()

which is O(n)

My program does read lines from text file as well (to process them), but the results are consistent (using the same text file): repeat removeLast(): 41-63 µs per function run subList clear: 67-81 µs per function run

function with `repeat removeLast()`:

private fun executeMove(move: Move) {
    with(move) {
        val sourceStack = stacks[fromStack]
        val destinationStack = stacks[toStack]

        val crates = sourceStack.takeLast(numberOfCrates)
        repeat(numberOfCrates) { sourceStack.removeLast() }
        destinationStack.addAll(crates)
    }
}

function with `subList clear()`:

private fun executeMove(move: Move) {
    with(move) {
        val sourceStack = stacks[fromStack]
        val destinationStack = stacks[toStack]

        val crates = sourceStack.takeLast(numberOfCrates)
        val sourceStackSize = sourceStack.size
        sourceStack.subList(sourceStackSize - numberOfCrates, sourceStackSize).clear()
        destinationStack.addAll(crates)
    }
}

(That's part of the solution to Advent of Code 2022 day 5)

Both

sourceStack

and

destinationStack

are

ArrayDeque<Char>

Which implements

AbstractMutableList

I also must admit, that the

repeat { removeLast() }

is a bit more readable than

subList().clear()

Thanks for checking!