171. Excel Sheet Column Number

public class Solution {    public int titleToNumber(String s) {        int len=s.length();        int sum=0;        int x=1;        len--;        while(len>=0){            sum+=(s.charAt(len)-64)*x;            x*=26;            len--;            }        return sum;        }}

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 

My solution: