LeetCode/kt/integer-to-roman.kt

class Solution {
    companion object {
        private val SYMBOLS: List<Pair<Int, String>> =
            listOf(
                1000 to "M",
                900 to "CM",
                500 to "D",
                400 to "CD",
                100 to "C",
                90 to "XC",
                50 to "L",
                40 to "XL",
                10 to "X",
                9 to "IX",
                5 to "V",
                4 to "IV",
                1 to "I",
            )
    }

    fun intToRoman(num: Int): String =
        SYMBOLS.fold(num to StringBuilder()) { (num, sb), (value, symbol) ->
            when (num) {
                0 -> num to sb
                else -> {
                    val count = num / value

                    (1..count).forEach {
                        sb.append(symbol)
                    }

                    num % value to sb
                }
            }
        }.second.toString()
}