CODEWITHSUNDEEP
collectionskotlin
oreh
oreh

Reputation: 1191

Convert a HashMap into IntArray while filtering some keys

I'm trying to implement a simple algorithm in Kotlin which finds only unique numbers in an array.

I cannot figuring out how to convert the map into the uniqueArray with elements which values equals to 1.

val array: IntArray = intArrayOf(4, 7, 3, 3, 4, 5)
val map: HashMap<Int, Int> = HashMap()

for (x in array) map.merge(x, 1, {v, _ -> v + 1})

// convert the map into an IntArray
val uniqueArray: IntArray = ...

Upvotes: 0

Views: 427

Answers (2)

Marko Topolnik
Marko Topolnik

Reputation: 200196

Here's a complete algorithm that doesn't involve counting instances:

val input = intArrayOf(4, 7, 3, 3, 4, 5)

val duplicates = emptySet<Int>().toMutableSet()
val result = emptySet<Int>().toMutableSet()

for (it in input) {
    if (duplicates.contains(it)) {
        continue
    }
    if (!result.add(it)) {
        result.remove(it)
        duplicates.add(it)
    }
}

Upvotes: 1

michalbrz
michalbrz

Reputation: 3504

You can use filter and destructure entry into key and value as below:

val uniqueArray: IntArray = map
            .filter { (k, v) -> v == 1 }
            .keys
            .toIntArray()

Upvotes: 1

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