Odtnhj

I have 2 arrays (they are actually 2 dimensional but I don't think that is important for the question)

val arr1 = arrayOf<Char>('a', 'b', 'c', 'd', 'e', 'b')
val arr2 = arrayOf<Char>('z', 'y', 'x', 'w', 'v', 'u')

I'm trying to implement the following method

fun filter(predicate: (T?) -> Boolean): Collection<Char> ... 

The arrays above are simplified as contents of arr1 in the real code is a nullable generic (T?) but I'm guessing we can carry on like this for the question.

So what I am trying to do is apply the predicate to the first array and get the values from the corresponding indices from the 2nd.

So lets say I try

val res = obj.filter it == 'b' 

I would want to get a collection with 'y' and 'u' in it.

I've been going around the houses on this so I think I've missed the proper way. My last attempt was along the lines of (used flatten as it's a 2 dimensional array)

val newList = arr1.flatten().mapIndexedidx, it -> predicate

I could then use this to get the values from arr2 (assuming they always flatten consistently ?)

My question I guess is either

a) how do I get a list of the indexes using mapIndexed with the predicate
or
b) what is the better way to do it (I'm assuming I've taken the wrong approach tbh)

val result = (arr1 zip arr2)
 .filter (c1, _) -> predicate(c1) 
 .map (_, c2) -> c2 

Zip the lists and use extension

fun <Any> List<Pair<Any,Any>>.myfilter(c: Any): List<Any>
 val result: MutableList<Any> = mutableListOf()
 for(item in this)
 if(item.first == c)
 result.add(item.second)
 
 return result


fun main(args: Array<String>)
 val arr1 = arrayOf<Char>('a', 'b', 'c', 'd', 'e', 'b')
 val arr2 = arrayOf<Char>('z', 'y', 'x', 'w', 'v', 'u')

 val zipped: List<Pair<Char,Char>> = arr1 zip arr2

 print(zipped.myfilter('e'))