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

class Solution {public:    string convertToTitle(int n) {        string str;        int carry = 0;        int result = 0;        char c[2];        c[1] = '\0';        while(n>26){            carry = n%26;            if(carry == 0){               c[0] = 'Z';               n = n-26;            }else{               c[0] = carry + 'A'-1;            }            str = string(c) + str;            n = n/26;        }        if(n!=0){            c[0] = n + 'A' - 1;            str = string(c) + str;        }        return str;    }};