Excel Sheet Column Title

Problem Description

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

Key Insights

• Each column title corresponds to a number represented in a base-26 numeral system.
• The letters A-Z are treated as digits where A=1, B=2, ..., Z=26.
• After Z, the sequence continues as AA=27, AB=28, ..., AZ=52, BA=53, etc.
• The conversion requires handling the modulo and division carefully to map numbers to the right letters.

Space and Time Complexity

Time Complexity: O(log(columnNumber))
Space Complexity: O(1)

Solution

To convert the given number to its corresponding Excel column title, we can repeatedly divide the number by 26 and use the remainder to determine the corresponding character. The algorithm works as follows:

1. Initialize an empty result string.
2. While the columnNumber is greater than 0:
   • Decrement columnNumber by 1 to adjust for 0-indexing.
   • Calculate the remainder when columnNumber is divided by 26.
   • Convert the remainder to a character (A=1, ..., Z=26).
   • Prepend the character to the result string.
   • Update columnNumber by dividing it by 26.
3. Return the resulting string.

Code Solutions