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
使用ASCII码一一对应
def convert_to_title(n) ans = ‘‘ while n > 0 n -= 1 ans = (65 + n % 26).chr + ans n /= 26 end ans end
Leetcode 168 Excel Sheet Column Title
原文：http://www.cnblogs.com/lilixu/p/4625975.html