[Leetcode]Excel Sheet Column Number

Given a column title as appear in an Excel sheet, return its corresponding column number.

本质上是一个进制转换问题。

 

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