Related to question 

Given a column title as appear in an Excel sheet, return its corresponding column number.

For example:

A -> 1    B -> 2    C -> 3    ...    Z -> 26    AA -> 27    AB -> 28

Credits:

Special thanks to  for adding this problem and creating all test cases.

跟上题一样，26进制到10进制的转换。

1 class Solution { 2 public: 3     int titleToNumber(string s) { 4         int res = 0; 5         for (int i = 0; i < s.length(); ++i) { 6             res *= 26; 7             res += (s[i] - 'A'); 8             ++res; 9         }10         return res;11     }12 };