completed Linked-List-1

[yashhh-23]

No description provided.

[Copilot]

Pull request overview

Adds Java solutions for three Linked List LeetCode problems (reverse list, remove Nth from end, detect cycle start), aligning with the repository’s “Linked-List-1” problem set.

Changes:

• Added Floyd’s cycle detection solution for “Linked List Cycle II”.
• Added stack-based linked list reversal solution.
• Added two-pointer (dummy + fast/slow) solution for removing the Nth node from the end.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
Solution.java	Implements cycle detection and returns cycle entry node (Problem 3).
reverseLL.java	Implements linked list reversal using a stack (Problem 1).
removeNthnodefromLL.java	Implements remove-Nth-from-end using dummy + two pointers (Problem 2).

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[super30admin]

Reverse Linked List (reverseLL.java)

Strengths:

• Clear problem-solving approach using a stack
• Good comments explaining the methodology
• Correctly identified and fixed the cycle issue
• Proper handling of edge cases (empty list)

Areas for Improvement:

• Space complexity: The stack-based approach uses O(n) space. Consider learning the iterative two-pointer technique (as shown in the reference solution) which achieves O(1) space.
• Unnecessary operations: Setting curr.next = null inside the loop is redundant for all nodes except the last one.
• The dummy node approach adds complexity. You could simplify by checking if it's the first node being added.

Recommendation: Try implementing the iterative two-pointer approach as a follow-up exercise. It's more space-efficient and commonly expected in interviews.

VERDICT: PASS

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Remove Nth Node From End of List (removeNthnodefromLL.java)

Strengths:

1. Excellent implementation of the two-pointer technique - this is the optimal approach for this problem
2. Successfully achieves the follow-up requirement of one-pass solution
3. Smart use of a dummy node simplifies edge case handling (removing first node)
4. Clean code structure with meaningful variable names
5. Good comments explaining the approach

Areas for Improvement:

1. The initial while loop condition while(count <= n) could be more intuitive as while(count < n + 1) or for(int i = 0; i <= n; i++) to better express the n+1 step logic
2. Consider adding a brief comment explaining why fast pointer needs to be n+1 steps ahead (to land slow exactly at the node before the target)

Overall Assessment:
This is a solid, well-implemented solution that demonstrates good understanding of the two-pointer technique and handles all edge cases correctly. The solution is more efficient than the reference solution in terms of time complexity.

VERDICT: PASS

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Linked List Cycle II (Solution.java)

Strengths:

• Correct implementation of Floyd's cycle detection algorithm
• Clear comments explaining the approach
• Good use of descriptive variable names
• Constant space complexity achieved
• Clean and readable code structure

Areas for Improvement:

• Consider adding null checks for slow in the first while loop for defensive programming (though not strictly necessary for this algorithm)
• The boolean flag approach is good, but the solution could also simply check if (slow == fast) after the loop exits to determine if a cycle was found

Overall: This is a solid implementation that correctly solves the problem with optimal time and space complexity. The student's approach demonstrates good understanding of the Floyd's cycle detection algorithm.

VERDICT: PASS