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 

Credits:
Special thanks to @ifanchu for adding this problem and creating all test cases.

本质上是10进制到26进制的转换，但是1~26的映射不好操作，因此减1变成0~25的映射更好操作。

 1 class Solution { 2 public: 3     string convertToTitle(int n) { 4         string s; 5         int idx; 6         while (n > 0) { 7             --n; 8             idx = n % 26; 9             s.push_back(‘A‘ + idx);10             n /= 26;11         };12         reverse(s.begin(), s.end());13         return s;14     }15 };

[LeetCode] Excel Sheet Column Title