Intersection Of Two Arrays

Given two integer arrays nums1 and nums2, return an array of their intersection. Each element in the result must be unique and you may return the result in any order.

Source

package questions

import _utils.UseCommentAsDocumentation
import utils.shouldBeOneOf

/**
 * Given two integer arrays nums1 and nums2, return an array of their intersection.
 * Each element in the result must be unique and you may return the result in any order.
 *
 * [Source](https://leetcode.com/problems/intersection-of-two-arrays/)
 */
@UseCommentAsDocumentation
private fun intersection(nums1: IntArray, nums2: IntArray): IntArray {
    val result = mutableSetOf<Int>()
    val larger = if (nums1.size >= nums2.size) nums1 else nums2
    val smaller = if (larger === nums1) nums2 else nums1
    val positionMap = mutableMapOf<Int, MutableList<Int>>()
    smaller.forEachIndexed { index, i ->
        positionMap[i] = positionMap.getOrDefault(i, mutableListOf()).also {
            it.add(index)
        }
    }
    for (i in 0..larger.lastIndex) {
        val currentVal = larger[i]
        positionMap[currentVal]?.let { result.add(currentVal) }
    }
    return result.toIntArray()
}


fun main() {
    intersection(intArrayOf(1, 2), nums2 = intArrayOf(2, 1)) shouldBeOneOf listOf(intArrayOf(1, 2), intArrayOf(2, 1))
    intersection(intArrayOf(1, 2, 2, 1), nums2 = intArrayOf(2, 2)) shouldBeOneOf listOf(intArrayOf(2))
    intersection(intArrayOf(4, 9, 5), nums2 = intArrayOf(9, 4, 9, 8, 4)) shouldBeOneOf listOf(
        intArrayOf(9, 4),
        intArrayOf(4, 9)
    )
}

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Updated on 2021-11-02