168. 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

public class Solution {    public String convertToTitle(int n) {        if(n<=0)            return null;        int s=0;        String ss="";        while(n>0)        {            s=n%26;            n=n/26;            if(s==0)//考虑如果余数为0，则是出现了最后一个元素Z，需要特殊处理            {             char c='Z';             ss=String.valueOf(c)+ss;             n=n-1;//重点！n需要减1            }            else            {            char c=(char)(64+s);            ss=String.valueOf(c)+ss;            }        }        return ss;    }}