leetcode-Excel Sheet Column Number

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 

public class Solution {    public int titleToNumber(String s) {        int sum=0;        char []ch=s.toCharArray();        for(int i=0;i<ch.length;i++)        {        sum=26*sum+(ch[i]-'A'+1);         }        return sum;    }}