Excel Sheet Column Title

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 

利用+'A'强制转换为字符得到想要的字符，这时要n-1，先求余得到字符，在对n整除26。

public String convertToTitle(int n) {if(n<=0)return "";return convertToTitle((n-1)/26)+(char)((n-1)%26+'A');}