LeetCode in Kotlin
273. Integer to English Words
Hard
Convert a non-negative integer num to its English words representation.
Example 1:
Input: num = 123
Output: “One Hundred Twenty Three”
Example 2:
Input: num = 12345
Output: “Twelve Thousand Three Hundred Forty Five”
Example 3:
Input: num = 1234567
Output: “One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven”
Constraints:
0 <= num <= 231 - 1
Solution
import java.util.StringJoiner
class Solution {
private val ones = arrayOf(
"One ", "Two ", "Three ", "Four ", "Five ", "Six ", "Seven ", "Eight ", "Nine "
)
private val teens = arrayOf(
"Ten ",
"Eleven ",
"Twelve ",
"Thirteen ",
"Fourteen ",
"Fifteen ",
"Sixteen ",
"Seventeen ",
"Eighteen ",
"Nineteen "
)
private val twenties = arrayOf(
"Twenty ", "Thirty ", "Forty ", "Fifty ", "Sixty ", "Seventy ", "Eighty ", "Ninety "
)
fun numberToWords(num: Int): String {
if (num == 0) {
return "Zero"
}
val joiner = StringJoiner("")
processThreeDigits(joiner, num / 1000000000, "Billion ")
processThreeDigits(joiner, num / 1000000, "Million ")
processThreeDigits(joiner, num / 1000, "Thousand ")
processThreeDigits(joiner, num, null)
return joiner.toString().trim { it <= ' ' }
}
private fun processThreeDigits(joiner: StringJoiner, input: Int, name: String?) {
val threeDigit = input % 1000
if (threeDigit > 0) {
if (threeDigit / 100 > 0) {
joiner.add(ones[threeDigit / 100 - 1])
val hundred = "Hundred "
joiner.add(hundred)
}
if (threeDigit % 100 >= 20) {
joiner.add(twenties[threeDigit % 100 / 10 - 2])
if (threeDigit % 10 > 0) {
joiner.add(ones[threeDigit % 10 - 1])
}
} else if (threeDigit % 100 >= 10 && threeDigit % 100 < 20) {
joiner.add(teens[threeDigit % 10])
} else if (threeDigit % 100 > 0 && threeDigit % 100 < 10) {
joiner.add(ones[threeDigit % 10 - 1])
}
if (name != null) {
joiner.add(name)
}
}
}
}