LeetCode-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 ret;
        while(num>999){
            ret.append("M");
            num-=1000;
        }
        if(num>899){
            ret.append("CM");
            num-=900;
        }
        
        if(num>499){
           ret.append("D");
           num-=500;
        }
        if(num>399){
            ret.append("CD");
            num-=400;
        }
        while(num>99){
            ret.append("C");
            num-=100;
        }
        
        if(num>89){
           ret.append("XC");
           num-=90;
        }
        if(num>49){
            ret.append("L");
            num-=50;
        }
        if(num>39){
           ret.append("XL");
           num-=40;
        }
        while(num>9){
            ret.append("X");
            num-=10;
        }
        
         if(num>8){
            ret.append("IX");
            num-=9;
        }
        if(num>4){
            ret.append("V");
            num-=5;
        }
        if(num>3){
            ret.append("IV");
            num-=4;
        }
        while(num>0){
            ret.append("I");
            num-=1;
        }
        return ret;
    }
};