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 

Analyse：十进制转换为二十六进制，用A~Z来表示。

 1 class Solution {
 2 public:
 3     string convertToTitle(int n) {
 4         string result;
 5         while(n){
 6             result += (--n) % 26 + 'A';
 7             n /= 26;
 8         }
 9         reverse(result.begin(), result.end());
10         return result;
11     }
12 };

Runtime: 12ms

 1 class Solution {
 2 public:
 3     int titleToNumber(string s) {
 4         int result = 0;
 5         for(int i = s.length() - 1, j = 0; i >= 0; i--, j++){
 6             result += ((s[i] - 'A' + 1) * pow(26, j));
 7         }
 8         return result;
 9     }
10 };