12. Integer to Roman

最近发现优快云上的垃圾信息太多了，一些兄弟什么玩意都往上边贴，搞得遇到问题检索时将优质答案隐没在了茫茫大海之中，效率太低，以及拷贝严重。

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"

Example 2:

Input: 4
Output: "IV"

Example 3:

Input: 9
Output: "IX"

Example 4:

Input: 58
Output: "LVIII"
Explanation: L = 50, V = 5, III = 3.

Example 5:

Input: 1994
Output: "MCMXCIV"
Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.

solution（简单才是优雅）

以下解答取自leetcode 高赞答案

class Solution {
    public 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];
    }
}

原链接：https://leetcode.com/problems/integer-to-roman/discuss/6274/Simple-Solution