168. Excel Sheet Column Title

Problem:

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 
    ...

Example 1:

Input: 1
Output: "A"

Example 2:

Input: 28
Output: "AB"

Example 3:

Input: 701
Output: "ZY"

Analysis:
To get "Z", we need to use 'A' + number. The number should be 25. So we have 'A' + (26 - 1) % 26.

Solution:

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