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 

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

public class Solution {

    public int titleToNumber(String s) {        

    }

}

该题和

Excel Sheet Column Title

 对应，不过是反过来了，给你一个excel列的名字，返回起列数。

    public static int titleToNumber(String s) {
    	if(s==null) return 0;
    	int result=0;
        for(int i=s.length()-1;i>=0;i--){
        	result +=Math.pow(26, s.length()-1-i)*(s.charAt(i)-'A'+1);
        }
        return result;
    }