leetcode[171]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 n=s.length();
        int res=0;
        for(int i=0;i<n;i++)
        {
            int tmp=s[i]-'A'+1;
            res=26*res+tmp;
        }
        return res;
    }
};