## The challenge

Create a function taking a positive integer as its parameter and returning a string containing the Roman Numeral representation of that integer.

Modern Roman numerals are written by expressing each digit separately starting with the left most digit and skipping any digit with a value of zero. In Roman numerals 1990 is rendered: 1000=M, 900=CM, 90=XC; resulting in MCMXC. 2008 is written as 2000=MM, 8=VIII; or MMVIII. 1666 uses each Roman symbol in descending order: MDCLXVI.

Example:

 ``````1 `````` ``````conversion.solution(1000); //should return "M" ``````

Help:

 ``````1 2 3 4 5 6 7 8 `````` ``````Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1,000 ``````

Remember that there can’t be more than 3 identical symbols in a row.

More about roman numerals – http://en.wikipedia.org/wiki/Roman_numerals

## The solution in Java code

Option 1:

 `````` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 `````` ``````public class Conversion { public String solution(int number) { String romanNumbers[] = {"M", "CMXC", "CM", "D", "CDXC", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"}; int arab[] = {1000, 990, 900, 500, 490, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1}; StringBuilder result = new StringBuilder(); int i = 0; while (number > 0 || arab.length == (i - 1)) { while ((number - arab[i]) >= 0) { number -= arab[i]; result.append(romanNumbers[i]); } i++; } return result.toString(); } } ``````

Option 2:

 `````` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 `````` ``````public class Conversion { public String solution(int n) { final String[] digit = {"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"}; final String[] ten = {"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"}; final String[] hundred = {"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"}; final String[] thousand = {"", "M", "MM", "MMM"}; String result=""; result = thousand[n/1000] + hundred[n%1000/100] + ten[n%100/10] + digit[n%10]; return result; } } ``````

Option 3:

 `````` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 `````` ``````public class Conversion { public String solution(int n) { String[] strs = new String[n]; java.util.Arrays.fill(strs, "I"); String result = java.util.Arrays.toString(strs).replaceAll("[ \\[\\],]",""); result = result.replaceAll("[I]{5}","V"); result = result.replaceAll("[V]{2}","X"); result = result.replaceAll("[X]{5}","L"); result = result.replaceAll("[L]{2}","C"); result = result.replaceAll("[C]{5}","D"); result = result.replaceAll("[D]{2}","M"); result = result.replaceAll("D[C]{4}","CM"); result = result.replaceAll("[L]{4}","CD"); result = result.replaceAll("L[X]{4}","XC"); result = result.replaceAll("[X]{4}","XL"); result = result.replaceAll("V[I]{4}","IX"); result = result.replaceAll("[I]{4}","IV"); return result; } } ``````

## Test cases to validate our solution

 `````` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 `````` ``````import org.junit.Test; import static org.junit.Assert.assertEquals; public class ConversionTest { private Conversion conversion = new Conversion(); @Test public void shouldConvertToRoman() { assertEquals("solution(1) should equal to I", "I", conversion.solution(1)); assertEquals("solution(4) should equal to IV", "IV", conversion.solution(4)); assertEquals("solution(6) should equal to VI", "VI", conversion.solution(6)); } } ``````