171. Excel Sheet Column Number.py

'''
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
'''

class Solution:
    def titleToNumber(self, s: str) -> int:
        l = len(s)-1
        ans = 0
        for c in s:
            ans += (26**l)*(ord(c)-64)
            l-=1
        return ans