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 

Credits:
Special thanks to @ifanchu for adding this problem and creating all test cases.

public class Solution {
	public String convertToTitle(int n) {
		StringBuilder sb = new StringBuilder();
		while (n > 0) {
			int apd = n % 26;
			char c;
			if (apd == 0) {
				c = 'Z';
				n = n / 26 - 1;
			} else {
				c = (char) (apd + 'A' - 1);
				n = n / 26;
			}
			sb.append(c);
		}
		return sb.reverse().toString();
	}
}

[LeetCode]Excel Sheet Column Title