168、Excel Sheet Column Title

https://leetcode.com/problems/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 

class Solution {
    public: string convertToTitle(int n) {
       if (n == 0) { 
            return ""; 
        }
       return convertToTitle((n - 1) / 26) + (char)((n - 1) % 26 + 'A'); 
    }
}
;