How do you solve Excel Sheet Column Number on LeetCode?

Excel Sheet Column Number (LeetCode #171) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(1) space complexity. Key insight: Understanding how Excel columns map to numbers is crucial.

What is the brute force solution for Excel Sheet Column Number?

The brute force approach for Excel Sheet Column Number is Brute Force, with O(n) time complexity and O(1) space complexity. We can convert each character in the string to its corresponding value and then calculate the total value as if it were a base-26 number. This approach is straightforward but inefficient for longer strings. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Excel Sheet Column Number?

Excel Sheet Column Number uses the following concepts: Math, String. The recommended patterns to study are: Base Conversion, String Manipulation.

What are the interview tips for Excel Sheet Column Number?

Explain your thought process clearly as you write the code. Consider edge cases, such as the smallest and largest possible inputs. Practice converting between different bases to strengthen your understanding.

What are common mistakes when solving Excel Sheet Column Number?

Forgetting to adjust the character value by subtracting 'A' and adding 1. Not considering the order of characters when calculating the result.

#171

Excel Sheet Column Number

Easy

MathStringBase ConversionString Manipulation

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n)	O(n)
Space	O(1)	O(1)

💡

Intuition

Time O(n)Space O(1)

The optimal solution is essentially the same as the brute force but emphasizes the mathematical properties of base-26 conversion. We can calculate the column number directly using a single pass through the string.

⚙️

Algorithm

3 steps

1Step 1: Initialize a variable to hold the result as 0.
2Step 2: Iterate through each character in the string from left to right.
3Step 3: For each character, calculate its value and update the result using the formula: result = result * 26 + (value of character).

solution.py5 lines

1def titleToNumber(columnTitle):
2    result = 0
3    for char in columnTitle:
4        result = result * 26 + (ord(char) - ord('A') + 1)
5    return result

ℹ

Complexity note: The time complexity remains O(n) as we still process each character once. The space complexity is O(1) since we use a fixed amount of space.

1Understanding how Excel columns map to numbers is crucial.
2Recognizing the base-26 nature of the problem helps in forming the solution.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.