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 

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

class Solution {
public:
    int titleToNumber(string s) 
    {
        int res=0;
        int n=s.length();
        if(n==0)
            return res;
        for(int i=0; i<n; i++)
            res = res*26+(s[i]-64);
        return res;
    }
};

LeetCode--Excel Sheet Column Number