Excel Sheet Column Number

Related to question Excel Sheet Column Title

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 

class Solution {
public:
    int titleToNumber(string s) {
        int result = 0;
        for(int i=0;i<s.length();i++){
            result = result*26 + s[i] + 1 - 'A';
        }
        return result;
    }
};