how do I make an integer to roman algorithm in dart? - dart

Question

I want to write an algorithm that converts integer numbers to roman numbers and supports any positive number in dart.
I can do this in Java using String builder and i tried to do it in dart but i failed.
so please if anyone could help me, that would be very much appreciated!
here is the java algorithm, maybe it would help:
public static int[] arabianRomanNumbers = new int[]{
1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1
};
public static String[] romanNumbers = new String[]{
"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"
};
public String intToRoman(int num) {
if (num < 0) return "";
else if (num == 0) return "nulla";
StringBuilder builder = new StringBuilder();
for (int a = 0; a < arabianRomanNumbers.length; a++) {
int times = num / arabianRomanNumbers[a]; // equals 1 only when arabianRomanNumbers[a] = num
// executes n times where n is the number of times you have to add
// the current roman number value to reach current num.
builder.append(romanNumbers[a].repeat(times));
num -= times * arabianRomanNumbers[a]; // subtract previous roman number value from num
}
return builder.toString();
}

Answer 1

StringBuilder is called StringBuffer in Dart and does nearly the same but with a little different interface which you can read more about in the API documentation:
https://api.dart.dev/stable/2.7.1/dart-core/StringBuffer-class.html
With this knowledge, I have converted your Java code into Dart:
const List<int> arabianRomanNumbers = [
1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1
];
const List<String> romanNumbers = [
"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"
];
String intToRoman(int input) {
var num = input;
if (num < 0) {
return "";
}
else if (num == 0) {
return "nulla";
}
final builder = StringBuffer();
for (var a = 0; a < arabianRomanNumbers.length; a++) {
final times = (num / arabianRomanNumbers[a]).truncate(); // equals 1 only when arabianRomanNumbers[a] = num
// executes n times where n is the number of times you have to add
// the current roman number value to reach current num.
builder.write(romanNumbers[a] * times);
num -= times * arabianRomanNumbers[a]; // subtract previous roman number value from num
}
return builder.toString();
}
void main() {
for (var i = 0; i <= 1000; i++) {
print('$i => ${intToRoman(i)}');
}
}