这个题就是给一个数(1-3999)转换为罗马计数，说简单不简单，说难不难。
附上百度百科：http://baike.baidu.com/link?url=TR8d0KXBBMWZffIDqBd_IFPSi0RZkB06DpUlsaZs-9_gCLNQaIVd2VmMwyf-3zG8
代码如下：

class Solution {
public:
    string intToRoman(int num) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        char schar[10];
        int index = 0;
        int count;
        if(num / 1000 != 0)
        {
            count = num / 1000;
            num = num % 1000;
            for(int i = 0;i < count;i++)
            {
                schar[index++] = 'M';
            }
        }
        if(num / 100 != 0)
        {
            count = num / 100;
            num = num%100;
            switch(count)
            {
                case 1:
                    schar[index++] = 'C';
                    break;
                case 2:
                    schar[index++] = 'C';
                    schar[index++] = 'C';
                    break;
                case 3:
                    schar[index++] = 'C';
                    schar[index++] = 'C';
                    schar[index++] = 'C';
                    break;
                case 4:
                    schar[index++] = 'C';
                    schar[index++] = 'D';
                    break;
                case 5:
                    schar[index++] = 'D';
                    break;
                case 6:
                    schar[index++] = 'D';
                    schar[index++] = 'C';
                    break;
                case 7:
                    schar[index++] = 'D';
                    schar[index++] = 'C';
                    schar[index++] = 'C';
                    break;
                case 8:
                    schar[index++] = 'D';
                    schar[index++] = 'C';
                    schar[index++] = 'C';
                    schar[index++] = 'C';
                    break;
                case 9:
                    schar[index++] = 'C';
                    schar[index++] = 'M';
                    break;
            }
        }
        if(num / 10 != 0)
        {
            count = num / 10;
            num = num%10;
            switch(count)
            {
                case 1:
                    schar[index++] = 'X';
                    break;
                case 2:
                    schar[index++] = 'X';
                    schar[index++] = 'X';
                    break;
                case 3:
                    schar[index++] = 'X';
                    schar[index++] = 'X';
                    schar[index++] = 'X';
                    break;
                case 4:
                    schar[index++] = 'X';
                    schar[index++] = 'L';
                    break;
                case 5:
                    schar[index++] = 'L';
                    break;
                case 6:
                    schar[index++] = 'L';
                    schar[index++] = 'X';
                    break;
                case 7:
                    schar[index++] = 'L';
                    schar[index++] = 'X';
                    schar[index++] = 'X';
                    break;
                case 8:
                    schar[index++] = 'L';
                    schar[index++] = 'X';
                    schar[index++] = 'X';
                    schar[index++] = 'X';
                    break;
                case 9:
                    schar[index++] = 'X';
                    schar[index++] = 'C';
                    break;
            }
        }
        if(num != 0)
        {
            count = num;
            switch(count)
            {
                case 1:
                    schar[index++] = 'I';
                    break;
                case 2:
                    schar[index++] = 'I';
                    schar[index++] = 'I';
                    break;
                case 3:
                    schar[index++] = 'I';
                    schar[index++] = 'I';
                    schar[index++] = 'I';
                    break;
                case 4:
                    schar[index++] = 'I';
                    schar[index++] = 'V';
                    break;
                case 5:
                    schar[index++] = 'V';
                    break;
                case 6:
                    schar[index++] = 'V';
                    schar[index++] = 'I';
                    break;
                case 7:
                    schar[index++] = 'V';
                    schar[index++] = 'I';
                    schar[index++] = 'I';
                    break;
                case 8:
                    schar[index++] = 'V';
                    schar[index++] = 'I';
                    schar[index++] = 'I';
                    schar[index++] = 'I';
                    break;
                case 9:
                    schar[index++] = 'I';
                    schar[index++] = 'X';
                    break;
                default:
                    break;
            }
        }
        schar[index] = '\0';
        string s = schar;
        return s;
    }
};