LemonadeChange.kt - master - uizadcz/Algorithm

/**
 * https://leetcode.com/problems/lemonade-change/description/
 *
 * At a lemonade stand, each lemonade costs $5.
 * Customers are standing in a queue to buy from you and order one at a time (in the order specified by bills).
 * Each customer will only buy one lemonade and pay with either a $5, $10, or $20 bill.
 * You must provide the correct change to each customer so that the net transaction is that the customer pays $5.
 *
 * Note that you do not have any change in hand at first.
 *
 * Given an integer array bills where bills[i] is the bill the ith customer pays,
 * return true if you can provide every customer with the correct change, or false otherwise.
 */
class LemonadeChange {
    fun lemonadeChange(bills: IntArray): Boolean {
        var ans = true
        var fives = 0
        var tens = 0

        bills.forEach { bill ->

            when (bill) {
                5 -> {
                    fives++
                }

                10 -> {
                    if (fives > 0) {
                        fives--
                        tens++
                    } else {
                        ans = false
                        return@forEach
                    }
                }

                20 -> {
                    when {
                        fives > 0 && tens > 0 -> {
                            fives--
                            tens--
                        }

                        fives >= 3 -> {
                            fives -= 3

                        }

                        else -> {
                            ans = false
                            return@forEach
                        }
                    }
                }
            }
        }

        return ans
    }
}