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

解答：

其实质是将26进制数转成十进制数字

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