String - 12. Integer to Roman

12. Integer to Roman

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.

**Symbol**       **Value**
I             1
V             5
X             10
L             50
C             100
D             500
M             1000

For example, two is written as II in Roman numeral, just two one's added together. Twelve is written as, XII, which is simply X + II. The number twenty seven is written as XXVII, which is XX + V + II.

Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not IIII. Instead, the number four is written as IV. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as IX. There are six instances where subtraction is used:

• I can be placed before V (5) and X (10) to make 4 and 9. 
• X can be placed before L (50) and C (100) to make 40 and 90. 
• C can be placed before D (500) and M (1000) to make 400 and 900.

Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999.

Example 1:

Input: 3 Output: "III"

思路：

使用两个数组，分别保存1000 ~ 1和其对应的罗马字母，然后用给定的输入不断的对比数字数组，同时拼接罗马字母。比如58，大于50，于是先把L加上，然后得到8，之后再找到5比8小，就再加上V，剩得3，就大于1，所以加I，2加I，1加I,结果就是LVIII。

代码：

java

class Solution {

    /*public static String intToRoman(int num) {
        String M[] = {"", "M", "MM", "MMM"};
        String C[] = {"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"};
        String X[] = {"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"};
        String I[] = {"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"};
        return M[num/1000] + C[(num%1000)/100] + X[(num%100)/10] + I[num%10];
    }*/
    
    public static String intToRoman(int num) {
        int[] values = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
        String[] strs = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};
        
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < values.length; i++) {
            while(num >= values[i]) {
                num = num - values[i];
                sb.append(strs[i]);
            }
        }
        return sb.toString();
    }
}