given a map with possibly repeated values, is the ...

# getting-started

[nkiesel]

given a map with possibly repeated values, is the following best way to reverse it (to a Map<V, List<K>>)

fun <K, V> Map<K, V>.reverse(): Map<V, List<K>> = entries.groupBy { it.value }.map { it.key to it.value.map { it.key } }.toMap()

[Dan Fingal-Surma]

entries.groupBy({ it.value }, { it.key })

[Dan Fingal-Surma]

last one here: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/group-by.html

[nkiesel]

Nice, thanks!

[Klitos Kyriacou]

btw I think the right terminology is "invert".