LeetCode 171. Excel Sheet Column Number

Description

https://leetcode.com/problems/excel-sheet-column-number/

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

Constraints:

  • 1 <= s.length <= 7
  • s consists only of uppercase English letters.
  • s is between “A” and “FXSHRXW”.

Explanation

each digit accelerates by 26

Python Solution

class Solution:
    def titleToNumber(self, s: str) -> int:
        
        s = s.upper()
        number = 0

        for ch in s:
            number = number * 26
            number += ord(ch) - ord('A') + 1

        return number
  • Time complexity: ~N
  • Space complexity: ~1

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