Write a number in Roman numerals
A film credit or a chapter heading wants MCMXCIV rather than 1994.
- The subtractive forms count: 4 is IV, 9 is IX, 40 is XL, 90 is XC, 400 is CD, 900 is CM.
- Only 1 to 3999 can be written; anything outside gives an empty string.
toRoman(amount: int) → string
Java needs a compiler and Drill does not host one yet, so this page is the reference rather than an exercise: the problem, worked examples, and the solution in full. To type it out, the same problem runs in Python.
Where you start
String toRoman(int amount) {
}Worked examples
| Call | Result |
|---|---|
toRoman(1) | "I" |
toRoman(4) | "IV" |
toRoman(14) | "XIV" |
toRoman(1994) | "MCMXCIV" |
Hint
Keep the values and their symbols in one descending table, including the subtractive pairs. Then it is one greedy pass.
Reference solution in Java
String toRoman(int amount) {
if (amount < 1 || amount > 3999) return "";
int[] vals = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
String[] syms = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};
int n = amount;
StringBuilder sb = new StringBuilder();
for (int i = 0; i < vals.length; i++) {
while (n >= vals[i]) { sb.append(syms[i]); n -= vals[i]; }
}
return sb.toString();
}