[LeetCode] Integer to Roman

Given an integer, convert it to a roman numeral.

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

罗马数字是由字符I,V,X,L,C,D,M等等表示的，其中
I = 1;
V = 5;
X = 10;
L = 50;
C = 100;
D = 500;
M = 1000;
接下来应该是V开始的重复，但是上面要加一个横线，表示对应数字的1000倍。
个位应该是：I,II,III,IV,V,VI,VII,VIII,IX
十位应该是：X,XX,XXX,XL,L,LX,LXX,LXXX,XC
百位应该是：C,CC,CCC,CD,D,DC,DCC,DCCC,CM

千位就是：  M,MM,MMM

从高位到地位取值，然后把字符串拼凑起来即可。

string romans[4][10] =
{
    {"","I", "II","III","IV","V","VI","VII","VIII","IX" },
    {"","X","XX","XXX","XL","L","LX","LXX","LXXX","XC"},
    {"","C","CC","CCC","CD","D","DC","DCC","DCCC","CM"},
    {"","M","MM","MMM"}
};

class Solution {
    public:
        string digitToRoman(int digit, int pow)
        {
            return romans[pow][digit];
        }   

        string intToRoman(int num)
        {
            int base = 1000;
            int digit = 0;
            int pow = 4 - 1;
            string result;

            while(num)
            {
                digit = num/base;
                result += digitToRoman(digit, pow);
                num = num%base;
                base /= 10;
                pow --;
            }
            return result;

        }
};