12. Integer to Roman

看程序就知道思路了，很简单的思路。

class Solution {public:    string intToRoman(int num) {        int nint[21] = {1,2,3,4,5,9,10,20,30,40,50,90,100,200,300,400,500,900,1000,2000,3000};        string sRoman[21] = {"I","II","III","IV","V","IX","X","XX","XXX","XL","L","XC","C","CC","CCC","CD","D","CM","M","MM","MMM"};        string sAns;        int i=20;        while(num > 0)        {            while(nint[i] > num )            {                i--;            }            num -= nint[i];            sAns += sRoman[i];        }        return sAns;    }};