171. Excel Sheet Column Number

problem

​​171. Excel Sheet Column Number​​

sum( (s[i]-'A'+1)*pow(26, i) )

code

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

1. ​​Leetcode_Excel Sheet Column Number​​;