168. Excel Sheet Column Title (Math)

Given a positive integer, return its corresponding column title as appear in an Excel sheet.

For example:

1 -> A
    2 -> B
    3 -> C
    ...
    26 -> Z
    27 -> AA
    28 -> AB

class Solution {
public:
    string convertToTitle(int n) {
        //residue is the value of current bit (from least-significant bit)
        //divided by 26, then iterate
        int residue = n%, quotient=n;
        string ret = "";
 
        while(quotient>){
            if(residue==) {
                residue = ;
                quotient -= ;
            }
            ret = (char)('A'+residue-) + ret;
 
            quotient /= ;
            residue = quotient %;
        }
 
        return ret;
    }
};