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 

public class Solution {

    public String convertToTitle(int n) {

        if(n<=0) return "";

        String s = "";

        while(n>=1) {

            s = ((char) ((n-1)%26 + 'A'))  + s;

            n = (n-1)/26;

        }

        return s;

    }

}