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) {        if (s.length() == 0 || s == null)            return 0;        int sum = 0;        for (int i = 0; i < s.length(); i++) {            sum = sum * 26 + (s.charAt(i) - 'A' + 1);        }        return sum;    }}