5.Excel Sheet Column Number

Example 1:
Input: "A"
Output: 1

Example 2:
Input: "AB"
Output: 28

Example 3:
Input: "ZY"
Output: 701

Solution:

Formula: 26^len * char + 26^len-1 * char + 26^len-2 * char + .......... + 26^0*char

class Solution
{
public:
    int titleToNumber(string s)
    {

        int l = s.length() - 1;
        int res = 0;
        for (int i = 0; i < s.length(); i++)
        {
            int x = pow(26, l) * (s[i] - 64);
            l--;
            res = res + x;
        }
        return res;
    }
};