Search code examples
kotlindistinct-values

Turn a list into a distinct list and map indices

I have a List of Objects, and I want to turn it into a distinct list while mapping all indices to the new indices.

Example:

List: ["a", "b", "a", "d"] -> ["a", "b", "d"]

Map: 

{
  0: 0, //0th index of original list is now 0th index of distinct list
  1: 1,
  2: 0, //2nd index of original list is now 0th index of distinct list
  3: 2  //3rd index of original list is now 2th index of distinct list
}

Is there a simple way to do this with a one-liner or with a fairly simple solution in kotlin?

Solution

  • The following expression will do that:

    val p = listOf("a", "b", "a", "d").let {
  val set = it.distinct().mapIndexed { i, v -> v to i }.toMap()
  it.mapIndexed { i, v -> i to set.getValue(v) }
}.toMap()