fun <T : Comparable<T>> intersectSorted(
    first: Iterable<T>,
    second: Iterable<T>
) = intersectSorted(first, second, naturalOrder())

fun <T> intersectSorted(
    first: Iterable<T>,
    second: Iterable<T>,
    comparator: Comparator<T>
): List<T> {
    val iter1 = first.iterator()
    val iter2 = second.iterator()
    return if (iter1.hasNext() && iter2.hasNext()) buildList {
        var it1 = iter1.next()
        var it2 = iter2.next()
        while (true) {
        	val cmp = comparator.compare(it1, it2)
        	if (cmp == 0) add(it1)
            if (cmp <= 0) it1 = if (iter1.hasNext()) iter1.next() else return@buildList
            if (cmp >= 0) it2 = if (iter2.hasNext()) iter2.next() else return@buildList
        }
    } else emptyList()
}