Is there any quick way to "reverse" map, so make a...

# announcements

[Marko Mitic]

Is there any quick way to "reverse" map, so make a Map<A, B> into Map<B, List<A>>?

[Marko Mitic]

Even better, Map<A, List<B>> into Map<B, List<A>>

[Egor Babarykin]

fun <A, B> Map<A, List<B>>.reverse(): Map<B, List<A>> = flatMap { it.value.map { v -> it.key to v } }
                    .groupBy({ it.second }, { it.first })