Integer to Roman

Given an integer, convert it to a roman numeral.

Input is guaranteed to be within the range from 1 to 3999.

Solution:

  1. public class Solution {
  2.   private char[][] romans = {
  3.     {'I', 'V', 'X'},
  4.     {'X', 'L', 'C'},
  5.     {'C', 'D', 'M'},
  6.     {'M', ' ', ' '}
  7.   };
  9.   public String intToRoman(int num) {
  10.     StringBuilder sb = new StringBuilder();
  12.     ArrayList<Integer> digits = new ArrayList<Integer>();
  14.     while (num > 0) {
  15.       digits.add(num % 10);
  16.       num /= 10;
  17.     }
  19.     int size = digits.size();
  21.     for (int i = size - 1; i >= 0; i--) {
  22.       String roman = getRoman(i, digits.get(i));
  23.       sb.append(roman);
  24.     }
  26.     return sb.toString();
  27.   }
  29.   private String getRoman(int level, int digit) {
  30.     char one  = romans[level][0];
  31.     char five = romans[level][1];
  32.     char ten  = romans[level][2];
  34.     StringBuilder sb = new StringBuilder();
  36.     if (digit == 9) {
  37.       sb.append(one).append(ten);
  38.     }
  40.     else if (digit >= 5) {
  41.       sb.append(five);
  42.       for (int i = 0; i < digit - 5; i++) {
  43.         sb.append(one);
  44.       }
  45.     }
  47.     else if (digit == 4) {
  48.       sb.append(one).append(five);
  49.     }
  51.     else {
  52.       for (int i = 0; i < digit; i++) {
  53.         sb.append(one);
  54.       }
  55.     }
  57.     return sb.toString();
  58.   }
  59. }