leetcode-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 

给定一个正整数，返回对应的Excel表头

实质上就是一个十进制对26进制的转换问题，注意26整数幂的特殊情况对应的行即可。

class Solution {
public:
    string convertToTitle(int n) {
        string res="";
        while(n>0)
        {
            int rest = n%26;
            n/=26;
            if(rest==0){
                n--;
                res='Z'+res;
            }else res= (char)('A'-1+rest)+res;
        }
        return res;
    }
};