LeetCode 168. Excel Sheet Column Title

Description

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

Given an integer columnNumber, return its corresponding column title as it appears in an Excel sheet.

For example:

A -> 1
B -> 2
C -> 3
...
Z -> 26
AA -> 27
AB -> 28 
...

Example 1:

Input: columnNumber = 1
Output: "A"

Example 2:

Input: columnNumber = 28
Output: "AB"

Example 3:

Input: columnNumber = 701
Output: "ZY"

Example 4:

Input: columnNumber = 2147483647
Output: "FXSHRXW"

Constraints:

  • 1 <= columnNumber <= 231 - 1

Explanation

Every 26 number repeats letter ‘A’ and base on the relationship with 26 to find the letter.

Python Solution

class Solution:
    def convertToTitle(self, columnNumber: int) -> str:
        
        result = ""
        
        while columnNumber > 0:
            result = chr(ord('A') + (columnNumber - 1) % 26) + result
            columnNumber = (columnNumber - 1) // 26
            
        return result
            
  • Time Complexity: O(N).
  • Space Complexity: O(N).

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