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) {
        int mp[100];
        int val[]={1000,900,500,400,100,90,50,40,10,9,5,4,1};
        string r[]={"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"};
        mp['I']=1;
        mp['V']=5;
        mp['X']=10;
        mp['L']=50;
        mp['C']=100;
        mp['D']=500;
        mp['M']=1000;
        
        int index=0;
        string result="";
        while(num>0)
        {
            while(num<val[index])
                index++;
            result=result+r[index];
            num=num-val[index];
        }
        return result;
    }
};