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