public String numberToBase26(int n) {
        StringBuffer buff = new StringBuffer();
        while (n > 0) {
            n--;
            buff.append((char)(n % 26 + 'A'));
            n = n / 26;
        }
        return buff.reverse().toString();
    }
Given a positive integer, return its corresponding column title as appear in an Excel sheet.
https://leetcode.com/problems/excel-sheet-column-title/
src/com/interview/misc/ConvertNumberIntoBase26.java