171. Excel Sheet Column Number - cocoder39/coco39_LC GitHub Wiki

171. Excel Sheet Column Number

    A -> 1
    B -> 2
    C -> 3
    ...
    Z -> 26
    AA -> 27
    AB -> 28 

AA = 1*26 + 1 = A*26 + A, how to make A = 1?

int titleToNumber(string s) {
        int res = 0;
        for (auto c : s) {
            res = res * 26 + (c - 'A' + 1);
        }
        return res;
    }