学步园

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 res = "";
		while(n)
		{
			res = (char)('A' + (n-1)%26) + res;
			n = (n-1) / 26;
		}
		return res;
    }
};