UNISERVO1

import kotlin.math.abs 

class Solution {
    fun findDuplicates(nums: IntArray): List<Int> {
        fun twiceFound(acc: Pair<List<Int>, MutableList<Int>>, num: Int): Pair<List<Int>, MutableList<Int>> {
            val (uniques, negs) = acc
            return if (negs[abs(num) - 1] < 0) {
                uniques.plus(num) to negs
            } else {
                negs[abs(num) - 1] = -1 * negs[abs(num) - 1]

UNISERVO1

class Solution {
    fun findDuplicates(nums: IntArray): List<Int> {
        fun twiceFound(uniques: MutableMap<Int, Int>, num: Int): MutableMap<Int, Int> {
            uniques.set(num, uniques.getOrPut(num){ 0 } + 1)
            return uniques
        }
        
        return nums.fold(mutableMapOf<Int, Int>(), { t, num -> twiceFound(t, num) }).toMap().filterValues{ it == 2 }.keys.toList()
        
    }

UNISERVO1

class Solution {
    val mask: Int = (0..31 step 2).fold(0){ acc, v -> acc + (1 shl v)}
    
    fun isPowerOfFour(num: Int): Boolean {
        return (num - 1) and num == 0 && (mask and num) > 0
    }
}

UNISERVO1

class Solution {
    fun isPalindrome(s: String): Boolean {
        val targetString: String = s.filter{ it.isLetterOrDigit() }.toLowerCase()

        return targetString == targetString.reversed()
    }
}

UNISERVO1

class MyHashSet() {
    
    val numBuckets: Int = 97
    val buckets = List<MutableSet<Int>>(numBuckets){ mutableSetOf<Int>() }
    val hashFunc : (Int) -> Int = { key: Int -> key % numBuckets }
    
    fun add(key: Int) {
        buckets.get(hashFunc(key)).add(key)
    }

UNISERVO1

class Solution {
    fun detectCapitalUse(word: String): Boolean {
        return word.all{ it.isLowerCase() } || 
                word.all{ it.isUpperCase() } || 
                (word.first().isUpperCase() && word.drop(1).all{ it.isLowerCase() })
    }
}