Given an integer, convert it to a roman numeral.

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

分析：这道题参考leetcode.pdf的解法，代码简洁，处理的巧妙。值得借鉴的几点如下：

（1）将1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1作为基数，从而不用单独处理900,400,90,40,9,4等特殊的情况。

（2）从大的基数开始计算，更简单，因为底数只有13个且最大值为3999，此种方法是可行的。

class Solution {public:    string intToRoman(int num) {        int radix[] = {
   1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};        string symbol[] = {
   "M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};        string result;                for(int i = 0; num > 0; i++){            int count = num/radix[i];            num %= radix[i];            while(count > 0){                result += symbol[i];                count--;            }        }        return result;    }};