171. Excel Sheet Column Number

Easy

---

Given a string columnTitle that represents the 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: columnTitle = "A"
Output: 1

Example 2:

Input: columnTitle = "AB"
Output: 28

Example 3:

Input: columnTitle = "ZY"
Output: 701

Constraints:

• 1 <= columnTitle.length <= 7

• columnTitle consists only of uppercase English letters.

• columnTitle is in the range ["A", "FXSHRXW"].

class Solution:
    def titleToNumber(self, columnTitle: str) -> int:
        length = len(columnTitle)
        index = 1
        col_num = 0
        for char in list(columnTitle):
            c_val = ord(char) - ord('A') + 1
            col_num += pow(26, length - index)*c_val
            index += 1
        return col_num