Excel Sheet Column Number (leetcode 171)

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 j = 0;
        for(int i = 0; i < s.size(); ++i) {
            j = j * 26 + (int)(s[i] - 'A' + 1);
        }
        return j;
    }
};