Two Combination Sum

TwoCombinationSum.kt

package org.kotlinlang.play
//Playground: https://pl.kotl.in/5Cjs0Zde6

fun main() {
    val k = 10
    val sample = arrayOf(1,1,2,23,4,9,13,6,9)
    
    val result = indexOfAddUp(sample, k)
    println(result)
}

fun indexOfAddUp(sample: Array<Int>, k: Int): List<List<Int>> {
    val result = mutableListOf<List<Int>>()
    val hashIndex = hashMapOf<Int, MutableList<Int>>()

    sample.forEachIndexed {index, number ->
        if (hashIndex.containsKey(number)) {
            val tempList = hashIndex[number]
            tempList!!.add(index)

            hashIndex[number] = tempList
        } else {
            hashIndex[number] = mutableListOf(index)
        }

        val diff = k - number

        if (hashIndex.containsKey(diff)) {
            val indexList = hashIndex[diff]
            val firstIndex = indexList!!.first()
            indexList.remove(firstIndex)

            hashIndex[diff] = indexList

            result.add(listOf(firstIndex, index))
        }
    }


    return result
}

In playground:

https://pl.kotl.in/5Cjs0Zde6