168.Excel Sheet Column Title(28 -> AB)

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

代码：
public class Solution {

    public String convertToTitle(int n) {

        String res = "";

    while(n!=0){

        res=(char)((n-1)%26+'A')+res;

        n = (n-1)/26 ; 

        }

    return res;

    }

}