```package leetcode import kotlin.collections.set...

# getting-started

[Sudhir Singh Khanger]

package leetcode

import kotlin.collections.set

fun main() {
    val nums1 = intArrayOf(1, 2, 2, 1)
    val nums2 = intArrayOf(2, 2)
    println(intersect(nums1, nums2).joinToString())
}

fun intersect(nums1: IntArray, nums2: IntArray): MutableList<Int> {
    val outputMap = hashMapOf<Int, Int>()
    val outputList = mutableListOf<Int>()

    for (i in nums1.indices) {
        if (nums1[i] in outputMap) {
            outputMap[nums1[i]]++
        } else {
            outputMap[nums1[i]] = 1
        }
    }

    for (i in nums2.indices) {
        if (nums2[i] in outputMap && outputMap[nums2[i]] > 1) {
            outputList.add(nums2[i])
            outputMap[nums1[i]]--
        }
    }

    return outputList
}

outputMap[nums1[i]]++ is complaining that No set method providing array access. I am not sure why.

[ephemient]

for (num1 in nums1) {
    outputMap[num1] = outputMap.getOrElse(num1) { 0 } + 1
}

[Sudhir Singh Khanger]

for (num2 in nums2) {
        outputMap[num2]?.let {
            if (it > 1) {
                outputList.add(num2)
                outputMap[num2] = it - 1
            }
        }
    }

Is nums2[i] in outputMap && outputMap[nums2[i]] > 1 not working because the pair may not exist or have been changed after checking containsKey.

Is there a way to improve the above code?

[tDnamein]

If you want an intersection, you could do this:

val nums1 = intArrayOf(1, 2, 2, 1)
val nums2 = intArrayOf(2, 2)

val setOfFirstArray =
        nums1.mapTo(hashSetOf()) { it }

 val intersection =
        nums2.filterTo(hashSetOf()) { n2 -> setOfFirstArray.contains(n2) }

This should even be quite efficient, since HashSet lookups are fast.

Please have in mind, that in my understanding an intersection contains each element only once. If you have a different understanding the code above won't work for you.

[Joel]

@tDnamein pretty sure this particular leetcode problem allows duplicates. There's always some catch in their problems.

[Sudhir Singh Khanger]

@Joel There are two problems 349. Intersection of Two Arrays I and 350. Intersection of Two Arrays II . The latter one requires duplicate.