171. Excel Sheet Column Number（LeetCode）

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 
还是接着上一篇，自己的“笨”方法：

class Solution {
public:
    int titleToNumber(string s) {
        map<char,int> m;
        string str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        for (int i = 1; i <= 26; i++)
        {
            cout << str[i - 1];
            m.insert(pair<char, int>(str[i - 1], i));
        }
        int len = s.size();
        int len1 = len;
        int sum1 = 0;
        for (int i = 0; i<len; i--)
        {
            int sum = 1;
            for (int i = 1; i < len1; i++)
            {
                sum *= 26;
            }
            sum1 += m[s[i]] * sum;
            len1--;
        }
        return sum1;
    }
};

别人的方法：

class Solution {
public:
    int titleToNumber(string s) {
        int result = 0;
        int carrier = 1;
        for (int i = 0; i < s.size(); i++) {
            result += (s[s.size() - i - 1] - 64) * carrier;
            carrier *= 26;
        }
        return result;
    }
};