Solved Reverse Linked List, Remove Nth Node From End of List and Linked List Cycle II

[anirudhv98]

Completed Linked-List-1, please review.

[super30admin]

Reverse a LinkedList (Problem1.cs)

Strengths:

• Correctly handles edge cases (null head)
• Proper use of O(1) space complexity
• Good comments explaining the approach
• Clean handling of pointer updates

Areas for Improvement:

• Variable naming: Consider using more conventional names like prev, curr, next instead of slow, medium, fast for better readability and alignment with common linked list terminology
• The comment could be more concise and focused on the key insight
• The algorithm is functionally correct but uses one more pointer than necessary (slow pointer is redundant as it's just medium's previous value)

Optimizations:
The solution could be slightly simplified by removing the slow pointer since it's always equal to medium.next before the update. However, the current approach is still valid and efficient.

VERDICT: PASS

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Remove nth node (Problem2.cs)

Strengths:

1. Excellent implementation of the two-pointer technique - a classic and efficient approach
2. Use of a dummy node is a best practice that elegantly handles edge cases like removing the head node
3. Clean, readable code with helpful comments
4. Achieves the optimal O(n) time complexity in a single pass, meeting the follow-up requirement
5. Proper memory management by setting temp to null (though in C# this isn't strictly necessary due to garbage collection, it shows good awareness)

Areas for Improvement:

1. The variable name temp for the deleted node is slightly misleading - it's not being used after null assignment. Consider naming it toDelete or simply removing this line entirely since it's not doing any functional work.
2. Could add a brief comment explaining why the dummy node is needed (to handle the case when removing the first node)

Overall, this is a well-crafted solution that demonstrates solid understanding of linked list manipulation and the two-pointer technique.

VERDICT: PASS

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Cycle in linked list (Problem3.cs)

Strengths:

1. Excellent implementation of Floyd's cycle detection algorithm
2. Clean, readable code with appropriate comments
3. Correct handling of edge cases (empty list, no cycle)
4. Optimal time and space complexity
5. The comment explaining the approach is clear and helpful

Areas for Minor Improvement:

1. The comment header format (Time/Space complexity, Leetcode status) is good but could include a brief explanation of why the algorithm works mathematically.
2. Consider adding a brief comment inside the while loop explaining the two-phase approach.

Note on Reference Solution Comparison:
The reference solution uses a boolean flag to track whether a cycle was found, while the student's solution uses an early return. Both approaches are valid and equivalent in terms of correctness and efficiency. The student's approach with early return is actually slightly more concise.

VERDICT: PASS