171. Excel Sheet Column Number

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 

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

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代码：

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