excel-sheet-column-number.py

#  https://leetcode.com/problems/excel-sheet-column-number/
#  Related Topics: Math
#  Difficulty: Easy

# Initial thoughts:
# This is like a base 26 number system where the alphabet letters represent 1 through 26.
# We need to convert their ascii code to the number they represent by subtracting 64 (since
# they are captical letters and A has the number 65)
# In addition we have to take care of their position. In a one letter "number", "A" represents
# 1, while if one letter is added to its right, it represents 26. This can be remedied by
# multiplying our number by 26 each time we calculate the value of a new letter and add it to it.

# Time complexity: O(n) where n === the length of s
# Space complexity: O(1)
from typing import List


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