12. Integer to Roman

Given an integer, convert it to a roman numeral.
Input is guaranteed to be within the range from 1 to 3999.

class Solution {public:    string intToRoman(int num) {        string a[] = {"","I","II","III","IV","V","VI","VII","VIII","IX"};        string b[] = {"","X","XX","XXX","XL","L","LX","LXX","LXXX","XC"};        string c[] = {"","C","CC","CCC","CD","D","DC","DCC","DCCC","CM"};        string d[] = {"","M","MM","MMM"};        return d[num/1000] + c[num/100%10] + b[num/10%10] + a[num%10];    }};