LeetCode 171 Excel Sheet Column Number
概述
https://leetcode.com/problems/excel-sheet-column-number/
解法
class Solution {
public:
    int titleToNumber(string columnTitle) {
        int ans = 0;
        for (auto c : columnTitle) {
            ans *= 26;
            ans += c - 'A' + 1;
        }
        return ans;
    }
};