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) 
    { 
        int result = 0; 
        for (int i = 0; i < s.length(); i++) 
        {
            result = result * 26 + (s.charAt(i) - 'A' + 1);       
        } 
        return result;         
    }   
}
//charAt() 方法返回指定索引处的char值。索引范围是从0到length() - 1。对于数组索引，序列的第一个char值是在索引为0，索引1