How do you solve Excel Sheet Column Title on LeetCode?

Excel Sheet Column Title (LeetCode #168) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(n) space complexity. Key insight: Understanding the mapping of numbers to letters is crucial, as it resembles a base-26 numeral system.

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

The brute force approach for Excel Sheet Column Title is Brute Force, with O(n²) time complexity and O(1) space complexity. The brute-force approach involves repeatedly subtracting the values of the letters from the column number until we reach zero. Each letter corresponds to a value (A=1, B=2, ..., Z=26), and we build the title from the end back to the start. The optimal Optimal Solution approach improves this to O(n).

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

Excel Sheet Column Title uses the following concepts: Math, String. The recommended patterns to study are: Mathematical conversions, String manipulation.

What are the interview tips for Excel Sheet Column Title?

Clearly explain your thought process while coding, as it shows your understanding of the problem. Be mindful of edge cases, such as the transition from Z to AA. Practice converting numbers to different bases to strengthen your understanding of numeral systems.

What are common mistakes when solving Excel Sheet Column Title?

Forgetting to decrement columnNumber before calculating the character, which leads to off-by-one errors. Not handling the transition from Z to AA correctly, which can confuse the logic.

#168

Excel Sheet Column Title

Easy

MathStringMathematical conversionsString manipulation

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n)
Space	O(1)	O(n)

💡

Intuition

Time O(n)Space O(n)

The optimal approach uses a mathematical understanding of the base-26 number system. Instead of building the string backwards, we directly compute the characters based on the column number's value.

⚙️

Algorithm

6 steps

1Step 1: Initialize an empty string to store the result.
2Step 2: While columnNumber is greater than 0, do the following:
3Step 3: Decrement columnNumber by 1 to adjust for zero-based indexing.
4Step 4: Calculate the character corresponding to the current columnNumber using modulo 26.
5Step 5: Prepend the character to the result string.
6Step 6: Update columnNumber by dividing it by 26.

solution.py7 lines

1def convertToTitle(columnNumber):
2    result = ''
3    while columnNumber > 0:
4        columnNumber -= 1
5        result = chr(columnNumber % 26 + 65) + result
6        columnNumber //= 26
7    return result

ℹ

Complexity note: The time complexity is O(n) because we loop through the digits of the base-26 representation of the column number, and the space complexity is O(n) for the resulting string.

1Understanding the mapping of numbers to letters is crucial, as it resembles a base-26 numeral system.
2The adjustment of columnNumber by subtracting 1 is necessary to align with zero-based indexing.

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