Understanding the ID Discrepancy in Leetcode’s /submit API Call

When working on coding platforms like Leetcode, developers often face various peculiarities in the system, especially when it comes to the data being sent and received via API calls. A recent question raised in the Leetcode community revolves around the discrepancy in question IDs during the /submit API call. Let’s dive into this issue, explore its implications, and clarify the underlying mechanics.

The Question at Hand

A user noticed that while submitting a solution to a specific problem, the question ID in the /submit API call did not match the expected ID. For example, they observed that for Problem 1, the question ID is correctly referenced as 1. However, when they checked for another problem, the ID differed. This raised the question: Is this a bug, or is there something more to it?

Investigation and Findings

To get to the bottom of this mystery, the user decided to dig deeper into the Network tab of their browser’s developer tools. What they discovered was quite enlightening: Leetcode utilizes two different identifiers for each question—questionId and questionFrontendId.

• questionId: This is the ID used internally by Leetcode’s backend.
• questionFrontendId: This is the ID that is presented to users on the frontend.

Through a binary search approach, the user pinpointed that the mismatch between these two IDs starts at Problem No. 700. This means that for all problems from 700 onwards, the questionId and questionFrontendId do not align.

Why This Matters

You might be wondering why this discrepancy exists and its implications for users. Here are a few points to consider:

1. Clarity in Problem Identification: For developers working on solutions, the mismatch can lead to confusion. If you’re trying to reference a problem by its ID, it’s crucial to know which identifier to use.

2. API Consistency: If the API behaves inconsistently, it could lead to errors in automated scripts or tools utilized by developers. Understanding these nuances is essential for effective coding and debugging.

3. Cross-Platform Development: If you are working in a specific programming language (like Rust, as one commenter pointed out), it’s essential to confirm whether this ID mismatch affects the language’s behavior or test case execution.

Community Insights and Additional Questions

In response to the original query, several community members posed important questions:

• Does question 2350 exist?: This question highlights the need for clarity regarding the existence of specific problems and their IDs.
• Does a similar issue occur for problems like 2240 and 2238?: This helps determine if the ID discrepancy is a widespread issue or specific to certain problems.
• Does this happen for all languages or just Rust?: Understanding if this is a language-specific issue could help isolate the problem.
• Does it run your code against the right test cases?: This is crucial for ensuring that submitted solutions are evaluated correctly.

These inquiries reflect the community’s engagement and eagerness to understand the intricacies of the Leetcode platform.

Conclusion

In conclusion, while the differing question IDs in Leetcode’s /submit API call might initially seem like a bug, they are rooted in the platform’s design. Recognizing the distinction between questionId and questionFrontendId is vital for developers to navigate the platform effectively. As with any coding platform, a deeper understanding of its mechanics can enhance the user experience and aid in troubleshooting.

If you have more questions or insights about this topic, feel free to share them in the comments below or check out the Leetcode forum for further discussion! Happy coding!