Excel sheet column number

Time: O(N); Space: O(1); easy

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: s = “A”

Output: 1

Example 2:

Input: s =“AB”

Output: 28

Example 3:

Input: s = “ZY”

Output: 701

[1]:

class Solution1(object):
    def titleToNumber(self, s):
        """
        :type s: str
        :rtype: int
        """
        result = 0

        for i in range(len(s)):
            result *= 26
            result += ord(s[i]) - ord('A') + 1

        return result

[2]:

sol = Solution1()
s = "A"
assert sol.titleToNumber(s) == 1
s = "AB"
assert sol.titleToNumber(s) == 28
s = "ZY"
assert sol.titleToNumber(s) == 701
s = "AAAB"
assert sol.titleToNumber(s) == 18280