Excel Sheet Column Number:有字母组成的26进制转换成10进制

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 

思路：26进制转换成10进制的按位运算，很简单，逐位累加求和即可。

class Solution {
    public int titleToNumber(String s) {
        if(s.length()==0) return 0;
        int sum = 0;
        int bit = 1;
        for(int i = s.length()-1;i>=0;i--){
            sum += ((int)(s.charAt(i)-'A')+1)*bit;
            bit *=26;
        }
        return sum;
    }
}