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 

public class Solution {    public int titleToNumber(String s) {        char arr[] = s.toCharArray();        int len = arr.length;        int num = 0;        if (len == 0){        return 0;        }        for (int i = 0; i < len; i ++){        num += (arr[i] - 64) * Math.pow(26, len - 1 - i);        }        return num;     }  }