168. Excel Sheet Column Title

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 


1->A  27->AA

C++(3ms):

class Solution {
public:
    string convertToTitle(int n) {
        string res = "" ;
        char tmp ;
        while(n){
            n -= 1 ;
            tmp = 'A' + n%26 ;
            res = tmp + res ;
            n /= 26 ;
        }
        return res ;
    }
};