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

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

• 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: C = 100, L = 50, XXX = 30 and III = 3.

Example 5:

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

題目大意：將一個整數轉化為羅馬數字表示法～

思路：因為輸入資料的範圍是1~3999，考慮把相應的 1 2 3 4 5 6 7 8 9 10 20 30 40 50 60 70 80 90 100 200 300 400 500 600 700 800 900 1000 2000 3000對應的羅馬數字符號分存入一個vector<vector<string>>中，然後根據實際數字的相應位取出相應字元放在結果字串前。

class Solution {
public:
    const static vector<vector<string>> table;
    
    //Input is guaranteed to be within the range from 1 to 3999.
    string intToRoman(int num) {
            string result;
            int count = 0;
            while (num > 0) {
                int temp = num % 10;
                result = table[count][temp] + result;
                num /= 10;
                count++;
            }
            return result;
    }
};
                                             
const vector<vector<string>> Solution::table = { { "", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX" }, //1 2 3 4 5 6 7 8 9
									   { "", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC" },  //10 20 30 40 50 60 70 80 90
									   { "", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM" }, //100 200 300 400 500 600 700 800 900
									   { "", "M", "MM", "MMM" } // 1000 2000 3000 
										  };