Excel Sheet Column Title

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 

------------------------- thinking -----------------------------------------------

very simple, but need to be very careful!!! Easy to fail at edge case!

we need to remember that each count should start from 0 instead of 1, so here n should always minus 1 for the correct index

------------------------- problems ------------------------------------------------

This question is a little different from natural number, because 0 cannot be the first digit of the number, while A is allowed to be at first one here! So be very careful for the while loop in the code, and n's updating in the loop!

------------------------- codes --------------------------------------------------

class Solution {
public:
    string convertToTitle(int n) {
        string result = "";
        n = n - 1;
        while (n >= 0) {
            result.insert(0, 1, 'A' + n % 26);
            n = n / 26 - 1;
        }
        //result.insert(0, 1, 'A' + n % 26);
        return result;
    }
};