QUESTION

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

FIRST TRY

string与数字的转换要借助char

class Solution {public:    int titleToNumber(string s) {        int ret = 0;        char ch;        for(int i = 0; i < s.length(); i++)        {            ch = s[i]; //string to char            ret = ret*26 + ch - 'A' + 1;        }        return ret;    }};