這個題其實是做26進制轉換

這個地方記得減大A，不是小a

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

https://blog.csdn.net/feliciafay/article/details/42332281

leetcode 171. Excel Sheet Column Number