Grouping and ordering the top 3 values in a list

April 6, 2022

I have a list similar in concept to the following:

val selectedValues = listOf("Apple", "Apple", "Apple", "Grape", "Grape", "Cherry")

I need a way to group and sort it so that I get something like this:

Apple: 3
Grape: 2
Cherry: 1

I got a little bit of headway with this answer but I want it to be ordered by the count (most to least) and I can’t seem to figure out how to get there.

I feel like the answer I posted gets me very close to what I want but I just need to figure out how to get it to work the way I need to and I’m just hitting a wall and need a little assistance as I’m still fairly new to Kotlin.

>Solution :

You could try something like this:

fun main(args : Array<String>) {
    val selectedValues = listOf("Apple", "Apple", "Apple", "Grape", "Grape", "Cherry")
    val solution = selectedValues
        .groupBy { it }
        .mapValues { it.value.size }
        .toList()
        .sortedByDescending { (_, value) -> value }
        .toMap()
    
   println(solution)
}

This will returns you