171. Excel Sheet Column Number

February 22, 2022

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"].

code

class Solution:
    def titleToNumber(self, columnTitle: str) -> int:
        res = 0
        for c in columnTitle:
            res = (ord(c) - ord('A') + 1) + res * 26
        return res

code

class Solution:
    def titleToNumber(self, s: str) -> int:
        val = 0
        length = len(s)
        for i in range(length):
            val += (ord(s[i]) - ord('A') + 1) * pow(26, length - 1 - i)
        return val

code

class Solution:
    def titleToNumber(self, s: str) -> int:
        return functools.reduce(
            lambda result, c: result * 26 + ord(c) - ord('A') + 1, s, 0
        )

lambda result, c: result * 26 + ord(c) - ord('A') + 1 is the func the parameter of reduce function is (func, seq, initial)