[LeetCode] 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

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 };