LeetCode 171 Excel Sheet Column Number

Problem:

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 

Summary:

将二十六进制数字转为十进制。

Analysis:

class Solution {
public:
    int titleToNumber(string s) {
        int len = s.size();
        int res = 0;
        
        for (int i = 0; i < len; i++) {
            res += (s[len - i - 1] - 'A' + 1) * pow(26, i);
        }
        
        return res;
    }
};