Solution to Stripe phone interview questions (you can find them here - https://leetcode.com/discuss/interview-question/2585038/Stripe-or-Phone-Screen-or-Senior-SE-or-Reject

stripe.kt

class OpeningTime {
    internal var isClosed = false
    internal val customerPresence: StringBuilder = StringBuilder()
}

fun computePenalty(log: String, closingTime: Int): Int {
    val logArray = log.split(" ")
    var penalty = 0
    for (i in logArray.indices) {
        if (i < closingTime) {
            if (logArray[i] == "N") penalty++
        } else {
            if (logArray[i] == "Y") penalty++
        }
    }
    return penalty
}

fun findBestClosingTime(log: String): Int {
    var smallestPenalty = Int.MAX_VALUE
    var bestClosingTime = 0
    val logArray = log.split(" ")
    for (i in 0..logArray.size) {
        val penalty = computePenalty(log, i)
        if (penalty < smallestPenalty) {
            smallestPenalty = penalty
            bestClosingTime = i
        }
    }
    return bestClosingTime
}

fun getAllClosingTimesOrderByBegin(log: String): List<Int> {
    val logParts: List<String> = log.split(" ")

    var indexOfCurrentPart = -1
    val correctOpeningTimes: MutableList<OpeningTime> = ArrayList()
    for (part in logParts) {
        when (part) {
            "BEGIN" -> { // when BEGIN create new opening time and update index to point to current window
                correctOpeningTimes.add(OpeningTime())
                indexOfCurrentPart = correctOpeningTimes.size - 1
            }
            "END" -> {  // when END mark the current window as closed and find last not closed window
                correctOpeningTimes[indexOfCurrentPart].isClosed = true
                indexOfCurrentPart = correctOpeningTimes.indexOfLast { !it.isClosed }
            }
            else -> {   // when part of opening time just add it to current window
                correctOpeningTimes[indexOfCurrentPart].customerPresence.append(part).append(" ")
            }
        }
    }
    return correctOpeningTimes.map { findBestClosingTime(it.customerPresence.toString().trimEnd()) }
}