[LintCode] Integer to Roman

Given an integer, convert it to a roman numeral.

The number is guaranteed to be within the range from 1 to 3999.

Clarification

What is Roman Numeral?

• https://en.wikipedia.org/wiki/Roman_numerals
• https://zh.wikipedia.org/wiki/%E7%BD%97%E9%A9%AC%E6%95%B0%E5%AD%97
• http://baike.baidu.com/view/42061.htm

Example

4 -> IV

12 -> XII

21 -> XXI

99 -> XCIX

1. Create a mapping between the roman symbols and their integer values.

2. Starting from the biggest symbol, check the number of this symbol needed

to construct the input integer. Add this many symbols to the result string builder if needed.

Subtract the added value from the input integer.

3. Proceed to the next biggest symbol and repeat step 2 until the input integer becomes 0.

 1 public class Solution {
 2     public String intToRoman(int num) {
 3         if(num <= 0) {
 4             return "";
 5         }
 6         int[] nums = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
 7         String[] symbols = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};
 8         StringBuilder res = new StringBuilder();
 9         int digit  = 0;
10         while (num > 0) {
11             int times = num / nums[digit];
12             num -= nums[digit] * times;
13             for ( ; times > 0; times--) {
14                 res.append(symbols[digit]);
15             }
16             digit++;
17         }
18         return res.toString();
19     }
20 }

Related Problems

Roman to Integer

Integer to English