Excel Sheet Column Number

Problem Description

Given a string columnTitle that represents the column title as appears in an Excel sheet, return its corresponding column number.

Key Insights

• Excel columns are represented in a base-26 numeral system.
• Each letter corresponds to a number: A=1, B=2, ..., Z=26.
• The position of each letter contributes to its value based on its position in the string.

Space and Time Complexity

Time Complexity: O(n) where n is the length of the string columnTitle.
Space Complexity: O(1) since we are using a constant amount of space.

Solution

To convert the Excel column title to its corresponding number, we can treat the string as a base-26 number. Each character in the string contributes to the total based on its position. Starting from the rightmost character, we multiply the value of each character by 26 raised to the power of its position (0-indexed). We then sum these values to get the final column number.

The algorithm can be summarized as follows:

1. Initialize a result variable to 0.
2. Iterate over each character in the string from left to right.
3. For each character, convert it to its corresponding number (A=1, B=2, ..., Z=26).
4. Update the result by multiplying the current result by 26 and adding the character's value.
5. Return the result.

Code Solutions