171. Excel Sheet Column Number

Given a string columnTitle that represents the column title as appears 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: columnTitle = "A"
Output: 1

Example 2:

Input: columnTitle = "AB"
Output: 28

Example 3:

Input: columnTitle = "ZY"
Output: 701

def titleToNumber(self, columnTitle: str) -> int:
	mul = 0
	res = 0
	for i in columnTitle[::-1]:
		res += 26**mul * (ord(i) - ord('A') + 1)
		mul += 1
	return res