62 lines
1.6 KiB
Kotlin
62 lines
1.6 KiB
Kotlin
class Solution {
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/**
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* Holds fixed mapping of roman numerals to their respective numeric value.
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*/
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private val values = mapOf(
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'I' to 1, 'V' to 5, 'X' to 10, 'L' to 50, 'C' to 100, 'D' to 500, 'M' to 1000
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)
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/**
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* Represents an accumulator for right fold when turning roman numeral into an integer value.
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* @property sum Holds the current sum of the accumulator.
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* @property next Holds the value of the previous roman numeral digit.
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*/
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private data class Accumulator(val sum: Int = 0, val next: Int = 0) {
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/**
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* @param it Current roman numeral digit.
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* @return Sign that is to be used when modifying sum of the accumulator.
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*/
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private fun sign(it: Int): Int = when (next > it) {
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true -> -1
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false -> 1
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}
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/**
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* @param it Currently processed roman numeral digit.
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* @return Correctly updated accumulator.
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*/
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fun update(it: Int): Accumulator = copy(sum = sum + sign(it) * it, next = it)
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}
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fun romanToInt(s: String): Int = s
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.map { values[it]!! }
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.foldRight(Accumulator()) { it, acc ->
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acc.update(it)
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}
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.sum
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}
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fun main() {
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val s = Solution()
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val tests = mapOf(
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"I" to 1,
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"II" to 2,
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"III" to 3,
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"IV" to 4,
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"V" to 5,
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"VI" to 6,
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"VII" to 7,
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"VIII" to 8,
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"IX" to 9,
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"X" to 10,
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"LVIII" to 58,
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"MCMXCIV" to 1994
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)
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tests.forEach { (num, i) ->
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check(s.romanToInt(num) == i) {
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"$num: ${s.romanToInt(num)} == $i"
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}
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}
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}
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