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 
    ...

Example 1:

Input: "A"
Output: 1

Example 2:

Input: "AB"
Output: 28

Example 3:

Input: "ZY"
Output: 701

一個找規律的數學題,找找規律就出來了

solution:

class Solution {
    public int titleToNumber(String s) {
        int ans = 0;
        char Letter = 'A';
        for (int i = 0; i < s.length(); i++) {
            double num = Math.pow(26, s.length() - 1 - i);
            int p = s.charAt(i) - Letter + 1;
            ans += num * p;
        }
        return ans;
    }
}