Sort ArrayList based on Another ArrayList in kotlin

Question

I have a list of String as below:-

val a = listOf("G", "F", "E", "D", "C", "B", "A")

I will get another list from the server. For example:-

val b = listOf("A", "G", "C")

List from the server may contain fewer elements or more elements but will not contain elements other than the first list.

So, after sorting output should be like

// G, C, A

Answer 1

You can use map and sorted to achieve that easily on the condition that a do not have repetition -

val a = listOf("G", "F", "E", "D", "C", "B", "A")
val b = listOf("A", "G", "C")
val there = b.map{ v -> a.indexOf(v)}.sorted().map{v -> a[v]}
println(there)

Output:: [G, C, A]

Alternate sorter way as pointed by @jsamol in comment -

val there = b.sortedBy { a.indexOf(it) }

Answer 2

You are not trying to sort, you are trying to filter

fun filterByServer(server: List<String>, local: List<String>)
        = local.filter { value -> server.contains(value) }

filter takes a predicate in this case if your local value is contained on the server list