LeetCode(171) Excel Sheet Column Number

题目如下：

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

分析如下：

处理26进制，逐个读入字符串中的每一个字符进行处理转换即可。和Excel Sheet Colum Title这道题目互逆，不过这道题目要更容易想一些。

我的代码：

//68ms
class Solution {
public:
    int titleToNumber(string s) {
        int sum = 0;
        int tmp = 0;
        for (int i = 0; i < s.length(); ++i) {
            tmp = s[i] - 'A' + 1;
            sum = 26 * sum + tmp;
        }
        return sum;
    }
};