[BUG] - 383. Ransom Note - incorrect space complexity

[jbulin]

LeetCode Username

jbulin

Problem Number, Title, and Link

383. Ransom Note https://leetcode.com/explore/learn/card/the-leetcode-beginners-guide/692/challenge-problems/4427/

Bug Category

Editorial

Bug Description

In the video solution, space complexity is computed incorrectly as O(k) which for k=26 is O(1). That would mean that for any input, the algorithm only uses constant memory. However, the size of the dictionary depends on log n.

Language Used for Code

None

Code used for Submit/Run operation

No response

Expected behavior

The space complexity should be, for example, O(k log n).

Screenshots

No response

Additional context

No response

[exalate-issue-sync]

LeetCode Support commented: Hello jbulin,

Thank you for reaching out and providing your insights on the space complexity analysis in the video solution for the problem "383. Ransom Note". We appreciate your attention to detail.

Understanding the nuances of space complexity can be challenging, especially when constants like k are involved, such as when they are fixed values (e.g., the number of letters in the alphabet). In general, such constants do not affect the asymptotic analysis as they are viewed as O(1) space. Could you please provide more details on your perspective about how the size of the dictionary depends on log n? This would help us understand and investigate your concern accurately.

In the meantime, if available, you might find it helpful to review other problem discuss boards for further insights into space and time complexities shared by the community.

We're here to help, so feel free to reach out with any more details or questions.

Best regards,
LeetCode Support Team

[jbulin]

Hello Support Team!

In the solution, we construct a HashMap that stores, for every letter of the alphabet, the number of occurences of that letter. The number of occurences is in O(n) so the number of bits to store it is in O(log n). Consider k=26 and imagine the input where the ransomNote consists of 2^1000 a's and the magazine is the empty string "". In this case, n is 2^1000, and we need to store this number in the HashMap. That requires log n = 1000 bits.

[exalate-issue-sync]

LeetCode Support commented: Hello,

Your reported issue has been relayed to our team for thorough investigation. We appreciate your patience as we work to address and resolve this matter. We will reach out to you when we have updates regarding the issue.

If you have any further questions or concerns in the meantime, please feel free to let us know.

Best regards,
LeetCode Support Team

[exalate-issue-sync]

Epiphania_Ekenimoh commented: Thank you for your time.

Your feedback has been used to enhance the problem. As a token of our appreciation, your LeetCode account has been credited with 100 LeetCoins.

If you have any more questions or additional feedback, please don't hesitate to let us know. Your continued support is invaluable to us!

Best regards,
The LeetCode Team