171. Excel Sheet Column Number

题目

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 

我的解法

public class Solution {
    public int titleToNumber(String s) {
        int res = 0;
        for(int i = 0; i < s.length(); i ++){
            res += Math.pow(26, i)*(s.charAt(s.length() - 1 - i) - 'A' + 1);
        }
        return res;
    }
}

算法分析：相当于26进制，换算即可。